random reboots usually indicate a bad memory stick. if you have multiple sticks in there, you can boot with one at a time and see if that is the problem. if it boots fine and then goes to BSOD, that may mean your video drivers (do you use matrox powerdesk?) are causing the problem, as many cards have drivers that initialize after windows has booted, matrox being one of them.
Check out http://support.microsoft.com/. They have a knowledge base and newsgroup you can check with. MS even has technical folks stop by the newsgroups to help out.
In Win2000 these types of problems are relegated to memory/hardware problems: they rarely happen. My only experience in these problems are: (1) Bad memory , (2) wrong hardware driver installed. Usually replacing the driver with the correct/updated one solves the problem. Less often the memory goes bad.
I just had this happed to me about 10 days ago. It turned out to be the Klez virus. Goto to Symantec and download the trial version of the software and run it. If you can't get Win2000 to startup then start it in safe mode with networking if you have a cable modem or dsl. There is a black screen before the Windows 2000 splash screen. You want to press F8 at this black screen to get the safe mode options. I ended up having 1000 or so infected files including the kernal. I had to re-install Win2000 to a fresh partition and have been reinstalling my progs ever since. Pain in the A__! Hope this helps.
This screensaver is great. It doesn't turn off when you move the mouse, only when you hit Esc. Download it onto someone else's computer, set for 5minutes, and enjoy.