From: Computerpilot on 01/02/2003
There are quite a few things that can cause this problem.
There are viruses (Magistr, for example) that will mess around with your BIOS settings and really cause problems. Make sure you have the most up-to-date virus software with up-to-date virus definitions to catch one of these culprits.
Next, you want to change your settins in the BIOS (del on startup) so that it boots in this order:
HDD (primary hard drive or HDD 0, or HDD 1)
This will save your settings so that you will not need to reset every time you restart your computer.
In addition, if your BIOS looses power while it is off, it will also reset your settings. The most typical cause of this is related to a bad motherboard battery. System clock getting behind all the time would indicate a problem with the battery and that it will probably need to be replaced.
Sometimes, the hard drives and CDROMs are cabled and 'jumpered' for 'cable select'. This is a small jumper that is set on the actual hard drive to determine if it is primary or your secondary drive (should the computer go to which drive on boot). This setting should be avoided as much as possible. It the jumper is set to 'cable select', it would be adviseable to change to primary or secondary.
The BIOS may be corrupt. I would not consider this unless you have exhausted all other options. In addition, I would seek professional help in this case (find your nearest nerd). You can do a BIOS update from the internet and this may fix any problems with the BIOS.
In rare cases, I have seen this problems with motherboards that are failing. I cannot pinpoint a specific brand yet but it is a possiblity. Though, it is not likely in your case.
Hope this helps.