Laptop troubleshooting forum: Toshiba Satellite A135 makes loud beeps (alarm) at startup

I have a Toshiba Satellite A135 S4528 laptop that makes a loud beeping noise when I try to turn it on. I am running 32-bit Vista.

Here is a video of what happens:
http://www.youtube.com/watch?v=OH5LjrhOlb8

I am able to press F2 to access the BIOS settings. (I think that is what I'm accessing). If I remain there for a while, the fan powers on as normal. This makes me think it's not a fan problem.

I tried replacing the RAM, but it didn't make a difference.

Eventually, I am able to boot up my system, but I don't know what fixes the situation. I just wait a while, try multiple times and eventually it boots normally. I never leave the PC on to see what happens if I leave it alone, as the sound is quite alarming and makes me think I should turn it off immediately. The last time the beeping started, I pressed F2 during the beeps and the OS then booted. Was it because I pressed F2 or was this just a coincidence? I've shut it down only once since then and upon powering on was able to successfully boot, so haven't had a chance to test this F2 button further.

I have had other problems with this laptop, but I don't know if they are related to this loud alarm and failure to start.

Other problems:

1) The fan on this machine has become very loud, but as far as I know cools the computer just fine. The computer has never shut down on me after becoming too hot. But could heat damage have occurred during the one-and-a-half years it has been noisy?

2) Since I purchased this machine, I have gone through five or six AC adapters. I don't know if my computer somehow breaks them or if Toshiba continually makes faulty adapters.

3) Recently, on occasion my computer thinks I am holding down the left arrow key. Pressing the Ctrl button immediately remedies this.

I can't find the beep codes for this laptop, but do they apply? This seems to be more of an alarm than a beep code.

The fan seems to work, the battery is fine, the RAM is okay, so could the alarm indicate a motherboard problem or a failing hard drive? If so, how do I check their health?

If anyone knows what the beeping means I would appreciate your advice.