Transferring your old hard drive to your new computer is a really good idea, for a number of reasons. First, it makes certain that none of your confidential data--credit card numbers, passwords--winds up in a garage sale, and eventually in the hands of a hacker. Secondly, it gives you two physically separate hard drives in the machine, which you can use as a quick and simple backup solution. Just copy your important files from one drive to the other, and you're now guaranteed that even if one drive craters, your backed-up data will still exist on the other drive. You can obtain inexpensive backup software that will automate this task. Finally, using your old hard drive gives you extra storage space for free!
But before we go any further, let me speak briefly on the subject of viruses. Frequently, people upgrade their new machines because the old one stopped working properly; however, the reason it stopped working properly was often due to an unsuspected virus infection. Viruses live on the hard drive; and if you transfer the old, virus infested hard drive to the new computer, you'll infect your new machine as well. Fortunately, there's an easy way to protect yourself. Your new computer probably came with a virus protection program already installed; make sure it's working properly, then visit the manufacturers website and update everything. In particular, make certain that the virus definitions are right up to date. A good antivirus program running on your new computer will detect and eliminate viruses on your old hard drive automatically. But that program must be there, and be working properly, and be up to date. If it isn't, you could easily wind up infecting your new machine with viruses.
With that said, installing the old drive in the new machine is quick and simple; but there are a few gotchas to keep in mind. First, lets open up your old machine and physically identify the old hard drive. Shut the machine off, pull the power plug out of the back of the old computer, and remove the computer access panel or cover. You're looking for a thin metal box, about 4 inches by six inches, and about an inch thick. That box is your hard disk drive, where all your data lives. There will be a ribbon cable attached to the back of the drive, which connects to the motherboard; and there will also be a 4 pin power plug, also connected to the back of the drive, which runs up to the power supply. The 4 pin power cable is polarised, so it will only connect one way; sadly, the data cable - the ribbon cable - is sometimes polarised, and sometimes not. This means that it IS possible to connect it backwards. However, take a close look at the data cable. It will have a thin red line along one edge of the cable. Make note of which edge of the socket the red line on the cable is aligned with, and connect it to your new machine the same way. Having made careful note of how the cable is connected, remove the power and data cables - they can be stiff, but they just pull straight out - disconnect the hard drive from the old computer and remove it.
A quick note about hard drives. Starting in 2004, a new way of connecting hard drives to computer motherboards started to emerge. Traditionally, hard drives have used a ribbon data cable, about 2 inches wide, to connect to the motherboard; this was known as a PATA cable, for Parallel ATA cable. This method is going away, in favour of a new type of cable and electrical topology known as SATA, which stands for Serial ATA. A SATA cable has a rubber exterior and is about the thickness of a pencil, as opposed to the broad, flat ribbon cable associated with the old PATA cables. SATA drives are faster, and are easier to connect; but your old hard drive will almost certainly be the old PATA ribbon cable.
However, your new computer will almost certainly use a Serial ATA hard drive. Fortunately, most optical drives, such as DVD burners and CD readers, still use the old PATA specification. The problem is that SATA is new, and the fine details of how it works still vary from motherboard to motherboard; hence, on some motherboards it is possible to have a mix of SATA and PATA drives controlled by the same primary controller, and on others it is not. For that reason, I'm going to suggest that you install your old PATA hard drive on the secondary controller, along with one optical drive. However, if your new computer already has two optical drives, then you cannot do that; in this case, it will be necessary to connect your old drive - in some fashion - to the primary controller. Depending on your motherboard, this may, or may not, be possible. You'll need to read the manual that came with the motherboard, and probably make some settings changes in the Bios as well. However, all of this only applies if your old hard drive is a PATA drive, and your new computer has a SATA drive. If your new computer is still using the older PATA technology - surprising, but possible - then just connect your old hard drive as a slave device on the primary controller.
Master, Slave, Primary controller, you ask? Ah, let me explain.
When the IDE (Independent Drive Electronics) specification was finalised about 15 years ago, it was decided that each manufacturer would handle his own drive data storage method internally, and supply a standard data signal to the motherboard. Further, it was decided that the drive controller - the chip that controls the flow of data from the drive to the motherboard - would control a maximum of two drives, and each drive would be referred to as either a Master or a Slave. As time went on and CD drives made their appearance, it was discovered that people needed more than two drives; and so it became customary for motherboard manufacturers to include two drive controller chips, which were then labelled primary and secondary. As a result, virtually all motherboards manufactured today have two drive controllers; and each drive controller is capable of controlling two drives. Hence, motherboards today can typically control a maximum of 4 IDE devices. These devices are identified as Primary Master, Primary Slave, Secondary Master, and Secondary Slave.
Your new machine will probably be using SATA technology on the primary side, and the older PATA technology on the secondary side. So you'll be connecting your older PATA drive to the secondary controller. However, the secondary controller will probably already have one device on it; an optical drive, such as a CD ROM or a DVD burner. This device will already be set as a Master device; but your old hard drive will likely also be set as a Master device, as well. The thing you must avoid is having two drives on the same controller jumpered the same way, i.e., two masters or two slaves on the same cable; so you'll need to change either the optical drive or your old hard drive to a slave device. Here's how to do it: on the broad, flat top of your old hard drive you'll see a bunch of printing, and hopefully, a diagram. On the diagram you'll see M or MA (for master) S or SL (for slave) and C or CS (for Cable Select). Cable Select allows the physical position of the drive on the cable to determine if it will be seen by the computer as a master or a slave drive. Dell uses this topology, but hardly anyone else does; so unless your machine is a Dell, you probably won't have to worry about it. Instead, look at the diagram and note the jumper position associated with the SL. That's how you're going to be jumpering the drive.
On the back of the drive, where the cable plugs in, you'll see a tiny array of 7 or 8 gold pins, with a black jumper (called a Berg connector) connected to one or two of those pins. This is the jumper array, which determines if your drive will be seen by the computer as a master, a slave, or a cable select drive. It's very likely that your old drive will be set to the 'master' position; refer to the picture printed on top of the drive and get yourself oriented. Now, remove that black jumper and position it over the set of pins marked 'slave' on the diagram. Congratulations! You've now re-jumpered your old hard drive as a slave device.
If you find the diagram on the hard drive confusing - or worse, missing - you could consider leaving the old hard drive alone, and instead re-jumpering the optical drive in your new computer as a slave device. The jumpers on optical drives are usually much more plainly marked than those on hard drives, but it does involve getting your fingers into some very tiny spaces. If you can do that, you might find it easier to rejumper the optical drive, and leave the old hard drive alone.
At this point, you should have one device jumpered as a master, and the other jumpered as a slave. Now, you need to physically mount the old hard drive in the new case; hopefully, there's an empty bay, but on some cheap new machines there isn't, and you'll have to improvise. If you haven't already done so, shut down your new machine normally; then physically remove the power plug from the back of the computer chassis. Now, with the power disconnected, attach the drive.
Once the drive is mounted securely, you'll need to connect a data cable to the drive. To do this, identify the optical drive on the machine, and find the ribbon cable coming out of the back. Follow it down to the motherboard with your fingers. On the way, you'll find a socket spliced into the ribbon cable; this is the socket you want to plug into the back of your old hard drive. If the ribbon cable going from the back of the CD drive to the motherboard doesn't have a socket on it - very common on cheaper machines - you'll need to replace the ribbon cable with one that will accommodate two drives. You can find a suitable replacement cable at just about any store that sells computer parts.
Remember how we had the data cable connected in the old machine? Hook it up the same way in the new machine, with the red mark on the cable on the same side of the hard drive. If you've forgotten, the most common - but not universal - way of connecting a cable to the hard drive is with the red mark on the cable closest to the center of the drive, and furthest from the outside edge.
The last thing you'll need to do is plug a spare power cable into the back of the old hard drive. This is a 4 pin polarised plug, and it's impossible to plug it in the wrong way. The color coding on the wires is red, two blacks, and a yellow wire. Typically, there will be some spares coming out of the power supply; find one, and hook it up. In the unlikely event that you have no spares, you can get a splitter or Y cable adapter at most computer stores.
At this point you've re-jumpered your old hard drive so that it's a slave drive, you've physically mounted it in your new machine, you've connected the ribbon data cable and you've plugged in the 4 pin power cord. Now, plug your new machine in and turn it on. Watch the screen; you should see the original hard drive in the new machine listed, followed by a space, followed by the optical device and the hard drive from your old computer.
Let the machine boot into windows, left click on my computer, and check the drive listings. You should see two hard disk drives; one will be the old drive from your old computer. If you don't, right click on 'my computer' and select 'manage' from the drop down menu. This will start the computer management console. On the left hand side, select 'disk management'; this will list all the drives found on your machine. If the drive from your old machine is not listed, it means you've got a basic configuration error; the parallel cable is backwards, or the drive is jumpered incorrectly, or the drive is not getting power. If it is listed, there will typically be an error message which will give you a hint as to the problem that windows is having. But typically, with most older drives, you won't need to venture into the management console; it usually is only an issue when you install a drive larger than 127 gigabytes, or thereabouts. Given that your older hard drive had windows 2000 on it, I'm guessing that it's in the 40 to 60 gig range.
At this point, assuming your drive is visible in My Computer, you're home free. The old hard drive still has the old operating system on it; but it will not affect the operation of your new machine, simply because the computer will always boot from the new hard drive first. The exception would be if the new hard drive died; at which point on start-up the BIOS would continue to look for a bootable device, find the old drive, and try to boot windows 2000 up. However it would not be real successful, because all sorts of other parameters - like the motherboard, processor, quantity and type of memory, and about 50 billion other things - would all be very different from your old machine. It would be very confusing, to say the least, and probably not at all successful. For this reason, at your convenience, you may want to delete the Windows folder from the old hard drive. Just make sure you've copied any important data from the Windows folder before you delete it. Alternately, you could simply reformat your old drive; but this will erase every scrap and smidgen of your old data.
So there you are - a quick guide to moving your old hard drive to your new machine! It's actually quite easy, and certainly worthwhile doing. I hope you come to appreciate the convenience and flexibility that two hard drives gives you. Enjoy!