I'll assume for now that this isn't a hardware problem. I'd also assume it isn't really a windows 2000 problem, but rather an application issue that is messing stuff up.
There is no way for anyone to really help you without more information. For example, when you say crashing, are applications crashing, or is the OS itself doing something (I don't know what that might be, since it never happened to me)? Is the video freezing? or random applications freezing? Does the mouse pointer still work? When you press the caps lock key does the caps lock light come on on your keyboard? Will it respond to ALT-ESC or ALT-TAB, or the WINDOWS key?
Are you running anti-virus software or a SW firewall?
Is there any information in the Systems manager (My Computer->Manage->Systems Tools->Event Viewer)? Are there mysterious system events happening?
I'm not sure what you mean when you say you are re-installing. Are you completely wiping the hard disk and actually starting over, or just doing repair stuff or re-installing OS files (leaving all the same applications).
Have you run virus scans, adaware, spybot and hijack this, to remove damaging/resource hogging software? (I push the use of adaware,spybot, and hijack this. If you've never used them, your computer is probably hosed)
Are you re-installing the same applications that originally caused the problems?
Do others have access to the computer?
Are you always on the internet (like a cable modem or DSL connection) without a software or hardware firewall?
Remember, the definition of insanity is doing the same thing over and over and expecting something different to happen.
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"I wish I had a nickel for every time Windows crashed. ... Oh yeah, I do!" Bill Gates