Computer Horrors.

I've been having horrible, nasty, and weird computer problems over the past week and I can't figure out exactly the main problem. In the past I've always been able to figure out and fix the various problems I've encountered. Now I'm stumped because it's like I'm having several different problems all at once. I've narrowed it down to either a dying motherboard or a screwed up Windows installation. It's been crashing several times a day. It'll crash and reboot when it's just sitting there with no applications running other than whatever Windows 2000 runs in the background. It also won't boot up properly. Sometimes when I start it all I get is a blank screen, I don't see any of the BIOS junk you typically see when you start a PC. And if starts normally then it might crash during Windows start up. This morning it crashed three times during boot up. The Application Log only shows those Zone Alarm related True Vector Engine error messages. I'm stumped. Tomorrow I'm going to put in my Linux harddrive and see if the thing behaves similarly. (And, yes, I backed up all my data.)