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Community Newsletter: Q&A forum: 4/28/06 Help, my computer randomly restarts

by: Lee Koo (ADMIN) April 26, 2006 4:35 PM PDT

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4/28/06 Help, my computer randomly restarts

by Lee Koo (ADMIN) ModeratorCNET staff - 4/26/06 4:35 PM


I have a Dell Dimension 4500 PC with a Pentium 4 2GHz processor. The computer has been randomly restarting.</b> It is not caused by using any one application, and it happens completely randomly; it doesn't matter if the computer has been on for 5 minutes or 3 hours. Also, the system clock is losing time (the time is always wrong and needs to be reset). I thought that the CMOS battery might be the problem, so I swapped it out for a new one, but there's been no change or improvement. Next, I thought it might be the power supply not having enough wattage (it is a 250W PSU). The PSU fan is barely blowing, and I thought it could be overheating. I haven't purchased a new PSU yet, because I'm not sure that is the problem. I have Norton AntiVirus 2006 installed, and a full system scan has not revealed any viruses. I have Windows XP SP2 and have all downloaded Fixes/Updates. The Microsoft Malware removal tool did not find anything either.

I bought this computer from a friend. She was not too discerning in her Internet usage and ended up having to reformat the hard drive and reinstall Windows XP due to viruses. Since then, I have utilized Ad-aware, antispyware, and Norton to clean up the computer. There are no more problems with the computer that point to viruses, other than this random system restarting and the system clock inaccuracy.

Submitted by: Derek B. of Chicago, Illinois



This doesn't sound like a software/malware issue. Given that you mentioned a format and reinstall of XP was part of what was done to the box when you got it, it's not generally likely that some malware might have survived, unless, of course, there's another partition on the hard drive that wasn't wiped out.

And while I (and most everyone else) considers Norton AV to be more or less useless, I can't recall any reports of it causing random reboots.

Just to be on the safe side, you may want to consult the Event Viewer to see if there are any clues in the logs as to why it's rebooting. Right-click on the My Computer icon and select Manage. This opens the Management Console. Switch to the Event Viewer and go through the three logs.

There IS one possibility, however, that can and quite frequently DID cause random reboots. About 3 or 4 yrs ago, there was a nasty virus that DID cause reboots - mostly while it was ATTEMPTING to gain access to a computer. The bugger was so badly written, when it tried to access and unprotected Windows machine via the Internet on RPC, it would often crash and reboot the PC being afflicted. The odds, however, are not good that this is your culprit. A good firewall should block these attacks and it hasn't been in circulation much lately.

Now then, let's look at the computer itself. The first thing that struck me was the power supply. 250 Watts for a Pentium 4 2.0 GHz chip and the rest of the system is MAJORLY WEAK!

Wimpy power supplies will cause problems if you're running any applications that require the CPU to work more than at idle. Also, if you've got a number of USB devices plugged into the computer, that also adds a drain to the already inadequate power supply. If memory serves me, those Intel P4 2 GHz chips were supposed to be paired with at least a 350+ W PSU. What was Dell thinking - besides the obvious (making profit)? Just to be on the safe side, you may want to consider replacing the PSU with one that's rated at least
400 Watts.

Another possible issue would be the CPU itself. Pentium 4 chips, especially of recent vintage, tend to run blazing hot. Heat + CPUs = BAD news. If something is not working on the cooling end - be it dust clogging a vent, a fan bearing gone bad and not spinning up to proper speed, etc..., it's a good bet there's bound to be problems.

To check this out, take note of where everything plugs into the back, then unplug everything and open the case. If you see a ton of dust bunnies in there, gently remove them with vacuum cleaner or a can of compressed air. Pay VERY close attention to any vents that are used for intake or exhaust of hot air going to or coming from the CPU, make sure the fan spins freely and isn't weighed down with a heavy layer of crud and make sure the heat sink is likewise cleaned out.

Once you've cleaned the box out, you might want to take a moment to look at the motherboard itself. Take a look at the capacitors - those are the small bits on the board that look somewhat like beer or soda cans. The tops of them should be slightly depressed on the top. Should you see they be bulging on the top, that may be a sign they've blown and are no longer any good. Depending on which ones and where they're located, these can cause problems similar to the ones you're experiencing. If this is the case - it's probably time for a new motherboard.

Many modern motherboards also support a "PC Health monitor" function. If you hit DEL (or F1 or F2 on some models) as you're booting and go into the BIOS, there may be an option to check the temp and how fast, if at all, the CPU fan is running. There may also be an auto-shutdown feature where the machine will shut itself off in the event the system gets to a certain temp. Check your owner's manual to see if this function is available.

If you don't have the PC health monitor feature, you will want to power up the computer while the case is open and check to make sure the fans are spinning up and pushing air. If they're not, then replace as needed.

As for the clock... Chances are the clock problems are caused by the frequent reboots - especially ones of this variety. As the CPU gets busy doing whatever task(s) it's got to do, it draws more power. When it gets to the max the power supply can put out, the available power drops and the motherboard reboots itself. This is a voltage spike... This can and usually does disrupt the clock. Fixing the power issue will fix the clock issue most of the time - unless the clock circuit's been damaged by the spikes. In which case, you'll probably need to activate Windows automatic time update function or get a 3rd party utility that keeps the clock synced with any number of atomic clocks around the world.

Submitted by: Pete Z.



Derek, there are a number of issues that could be causing this problem.

First, let me put your mind at ease regarding the slow power supply fan; Dell throttles the fan speed according to the temperature, in order to maintain a constant operating temp. They also do this with the CPU fan. A slow speed is not indicative of fan failure. The Dell failsafe mode is to run the fan at full speed, at which point your computer sounds like a Cessna preparing for takeoff. A really, really loud fan indicates that there's a problem with the temperature sensing circuitry; a quiet, but turning, fan is normal.

I'd be surprised if you have a virus or spyware issue; but to check, I would run an online virus scan. These really are the gold standard in verifying that there are no viruses on the machine; they won't remove them, but they will tell you whether or not you're infected, and with what, and at what location. I use the Norton online scan, as I feel it is the most comprehensive; but several other companies offer similar services. To scan for spyware I use Ad Aware, but again there are other products that are as good. I'd use Ad Aware to remove any spyware first, as the Norton online scan will find and flag - but not remove - the spyware.

The fact that the clock is constantly wrong and replacing the battery did not solve the problem, concerns me. I'm worried that you might have a motherboard with swollen capacitors. To troubleshoot the hardware I would power the machine down, unplug the power cord, and start by doing a close visual examination of all the capacitors on the motherboard. If you have any swollen capacitors, then you've identified the problem; and realistically it's time for a new motherboard, as the cost of removing and replacing the capacitors greatly exceeds the cost of a new motherboard. Capacitors should have an absolutely flat top and straight sides; they usually have an 'X' etched across the top. If the sides or the top are bulged, then you've got an answer - not a happy answer, but an answer. I mention this because many machines - not just Dell - dating from this time period had a problem with swollen capacitors.

Assuming there are no swollen caps, I'd then remove all non essential cards from the machine. This would include sound cards, TV cards, USB expansion cards, modems, and anything else that's in the PCI slots. The idea is to reduce the machine to the absolute minimum number of components that will still provide a (barely) functional computer. I would also remove all but one memory module, and disconnect the power and data lines from all but the primary hard drive. Of course, I'd also unplug any USB devices outside of the essentials. You should wind up with four cords connecting to the computer box; power cord, video cord, mouse, and keyboard. Everything else should be disconnected.

At this point, run the machine, and wait for it to crash. Hopefully, it's now stable. If it crashes, then I'd swap the remaining components in the machine - probably just the memory module and video card - for known good components. If it still crashes, then the problem is either the power supply unit or the motherboard; you could try swapping out the PSU for a known good unit, but my money is on the motherboard being the problem.

If the machine is now stable, then you need to add components back into the mix, one at a time, until you identify the culprit. Because the problem is random and can take hours to occur, this will be a long, drawn out procedure. When you add a card, it's important that you use it during the testing period; I once worked on a machine that had an internal DSL modem card that was just fine, until you hooked it up and surfed the web... at which point it would bluescreen windows 2000. The moral there is, don't just plug in the card and install the drivers; actually put it through its paces.

You may find that you have two components, either of which is fine on its own, but when used together causes the system to crash. This is why it's important that you use WHQL certified drivers for all peripheral components whenever possible. Windows XP will complain when you try to install a driver that doesn't have WHQL certification; whenever possible, use certified drivers.

Using this basic troubleshooting procedure - stripping the machine down to it's absolute minimal configuration, achieving stability, then adding components one at a time - is a useful method of identifying a defective component, and turning a troublesome machine into a useful one. I hope that you find this helpful, and that you wind up with a rock solid machine for many years to come!

Submitted by: Charles W.



The clock issue and the random rebooting are, in all likelihood, separate and unrelated issues. Let's deal with the potentially more serious issue first, the random rebooting.

Whenever a computer starts behaving erratically, one has to consider viruses, adware and spyware as likely culprits. By reformatting and scanning your drive with Norton AntiVirus and antispyware software, you took reasonable steps to rule out this possibility. However, if the culprit is spyware, it might have been bundled with a third-party software and thus reinstalled after you reformatted your hard drive. Also, because antispyware software is not nearly as good as its antivirus counterpart in identifying and removing offending agents, an undesirable entity might have evaded detection, or the scanning engine you used might have left active spyware components behind.

Taking into consideration the troubleshooting steps you have taken, as well as your concerns about a faulty power supply unit (PSU), it seems unlikely that malware is at the root of your problem. Still, you have to allow for the possibility, however small, that the rebooting issue and the PSU issue are also separate problems - in other words, that you are dealing with three separate issues, counting the inaccurate system clock. For the sake of thoroughness, it wouldn't hurt to check the following Knowledge Base article;en-us;894278

to see whether the random rebooting might be caused by the presence of a root kit. This is a simple way to rule out yet another causative agent before taking on more elaborated troubleshooting steps.

Now, the fact that you brought up the possibility of your PC overheating suggests that the PSU has been a source of concern for some time. It also points at an issue that needs to be addressed, whether or not it ultimately is the cause of the random rebooting.

The first thing you should do is to open the case of your Dimension and verify that all power cables are securely attached to their respective components. It is possible that when you opened your computer to replace the CMOS battery (or for any other thing, like adding a memory card), you might have accidentally pulled and loosened a power cable. A loose or otherwise damaged power cable would explain both the random rebooting and why the power supply unit fan is "barely blowing."

While you are at it, inspect the fans for heavy accumulation of dust, hair, or the presence of a foreign object obstructing the fan blades. Use a compressed gas product like Endust for Electronics Duster to gently blow off lint, dust, and other contaminants. Compressed gas dusters are available at most office and computer supply stores.

(Before working inside your computer, make sure you are properly grounded. Failure to do so might result in electrostatic damage to components. To learn more about necessary precautions, please visit the following Knowledge Base article:

If all power cables are secure and there is nothing physically obstructing the fans, you should disable Windows XP's Automatic Reboot. By default, Windows XP reboots whenever it encounters a system failure. Because of this, any error messages pointing at the cause of the failure may vanish before you get a chance to even realize they are there. To disable Automatic Reboot and see whether your operating system can pinpoint the problem, perform the following steps:

1. Right-click the My Computer icon (either on your desktop, in the Start menu, or within your Control Panel), then click Properties from the drop-down menu.
2. Once the System Properties window appears, click the Advanced tab, and then click the Settings button under Startup and Recovery.
3. The Startup and Recovery window appears.
4. In the System Failure section, remove the check from the box next to Automatically reboot, then click OK to return to the System Properties window.
5. Click OK to close the System Properties window. Restart your computer if prompted to do so.
If the random rebooting is being caused by a software conflict or a problem with your memory, Windows XP should now display an error message the next time the system crashes. Write down any error message exactly as it appears, and search the Windows XP Help and Support website

for more details as well as any known solution. If your issue is resolved, feel free to enable Automatic Reboot once again.

If you are unable to elicit any error messages, you should consider replacing the PSU as soon as possible, lest you end up with a costlier tragedy at hand. At this point, you might want to check Dell's Support webpage

and Dell's Community Forums

to find out whether other Dimension 4500 owners have encountered similar problems. If there was an issue with faulty PSUs (or memory chips, which can also cause this problem) in this particular line of Dell PCs, you might be able to get a free replacement even if your computer is no longer under warranty.

Ask your friend whether the computer is still covered by an extended warranty or service plan. This would be a good time to request a transfer of ownership, if you haven't done so already. That way, you'll be able to deal with Dell Support directly rather than through your friend. (Chances are the friendship will come to an abrupt end the first time you ask her to deal with Dell Support...) For more information on this subject, visit

If the issue persists even after replacing the power supply unit, you probably have a problem with your memory modules. Please refer to your computer's owner's manual and/or the Dell Support website for instructions on how to test your computer's memory.

As far as the loss of time in Windows XP, Dell Support document #RA1060115 discusses this issue and provides two possible solutions. The first involves downloading an installing a small utility called Time.exe to reset the time synchronization in your operating system. You can access this short article and the download link by visiting

I installed Time.exe several years ago, with mixed results. A better solution was installing a free utility called Rocket.Time that connects to atomic time servers in the Internet at intervals, and corrects your system clock as needed.

The latest version of this utility lacks the option to hide its taskbar icon. The interface is somewhat busier, too - an obvious attempt to encourage users to upgrade to the premium version of the software. Older versions with the hide icon option are still available, and you should be able to find one here:,fid,17628,00.asp

Rocket.Time is just one of many programs designed to keep your system clock accurate. It is simple, free, and doesn't use a lot of resources. If you would like advanced functions such as different time zones and alarms, you can upgrade to the paid version or look for other alternatives by visiting

and searching for "clock." But if all you need is something to keep your system clock accurate, you can't go wrong with Rocket.Time.

Good luck!

Submitted by: Miguel K. of Columbus, OH



Derek, this can be a hard problem to fix because it can be caused by just about anything in the computer, as well as software issues. So the approach is to go after the most common problems first. However, in your case you have reinstalled Windows and the problem happens randomly rather than with specific programs, so it is probably not a software issue.

The most likely cause of this, by far, is bad memory. The way to test memory is to download a self-booting memory test program, and the most respected programs are Memtest and Memtest86 (two now-different programs that evolved from a common root). You can find these at and They are free, and you can use either/both. Microsoft also actually has a very similar memory diagnostic that can be downloaded from the Microsoft web site.

To use these, note that the program that you download is not the actual test, but rather is a program that will make a self-booting test floppy diskette. After using the downloaded program to make this diskette, you reboot the system from the floppy. The program is self contained and does not run under any operating system, neither Windows nor even DOS. For systems without a floppy drive, a dot-ISO file is also available to make a bootable CD. Once you have the CD, you can use it to run the test on a system without a floppy drive. The test needs to run for a number of passes (will probably take several hours or overnight) with zero errors. If you get any errors at all, even just one, you have bad memory in your system, which you need to replace. This is very common, and is the most common cause of such crashes.

[One additional thought here, I think Id remove and reinstall (reseat) the memory modules before running the test. They may simply have worked lose or be making bad contact with the memory sockets.]

The next most common problem is the power supply. In a generic system, Id just suggest replacing the power supply, but you have a Dell system, which may use a proprietary power supply for which a replacement is available only from Dell (and given the age of the system, maybe not even from Dell). If a generic ATX standard power supply will fit, try one. However the cheap power supplies that come with cheap cases (and almost any power supply selling for less than about $30) are often pretty junky. Go for a quality replacement power supply, 350 watts or more, by Enermax, Acer, Antec, Thermatake, CoolerMaster or other good brands. A quality 350 watt supply will easily be more stable and reliable than a cheap 400 or 500 watt supply. You can almost judge the quality of a power supply by its weight and by looking at the size of the capacitors, transformers and heat sinks, visible through the fan openings.

Now Im going to get edgy, and this isnt for everyone, but power supply problems and random lockups are often caused by dust and dirt that have accumulated over the years. If you want to be aggressive, remove the power supply and let it sit for a day or two so that the capacitors have discharged. Open the power supply carefully, and use a can of compressed air and a paint brush to carefully clean (dust) the interior components. Reassemble. Dont do any more disassembly than necessary, and dont touch anything inside the supply except with compressed air and, if necessary, the brush bristles (usually compressed air alone is enough). This is not for everyone, but in a supply that is several years old the amount of dust can be staggering and can cause the type of problems that you are experiencing. With a proprietary unit where a replacement is either expensive or unavailable, sometimes you have to resort to disassembly / cleaning / repair rather than replacement.

[You mentioned that the power supply fan was running slow; this may either be normal, or it may be the problem: some power supplies have thermally controlled fans that are supposed to run slowly [=quiet] until and unless a thermal sensor becomes warm. But the sensor may not be sensing a part of the power supply that is overheating. Regardless, however, replacing just the fan inside a power supply, while possible, involves more issues than I can reasonably discuss here.]

There is a similar dust/dirt issue in the area of the CPU heatsink and CPU fan (if there is a separate CPU fan), and the solution there is basically the same type of cleaning with compressed air and possibly a brush. Its also possible that remounting the CPU with new thermal compound would help, however, most inexperienced users will cause more problems than they will solve if they attempt this. Cleaning the CPU heatsink and fan is usually all that is required. Not all Dell systems have a dedicated CPU fan, but fans do fail, as well as get hopelessly clogged with dust, so investigate that. A can of compressed air will usually work wonders.

While you are at it with the compressed air, blow out dust from the rest of the system, paying particular attention to the CPU chipset on the motherboard and, if there is one, its heatsink.

If these suggestions dont fix the problem, you are into a situation that becomes far more difficult to fix and that may not be economically repairable. The next most common problem is the motherboard, but there is no good way for an end-user to diagnose this other than by substitution. Plug-in cards (video, sound card, modem, LAN) can cause crashes, and even IDE drives on occasion. And, finally, although its rare (very rare, really) it could be a bad CPU. But memory is about 70% of these problems that are caused by hardware, and the power supply and cooling issues are most of the rest, so start there. One final comment, if the system is overclocked in any way, revert all of the settings and jumpers to their default positions. But with OEM systems like Dell, overclocking usually isnt possible anyway as it is with a home-built system and a retail motherboard.

Good luck, this should get you started in the right direction.

Submitted by: Barry W. of North Canton, OH

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