I had simmilar problems witn Win2K freezing so I upgraded hardware and went to WinXP. After 1 week reinstalling software I had the same problems return.
I was pointed to
www.badcaps.com where I found out that my old ABit VP6 motherboard had bad capacitors and described all the problems I was having (and that sounds simmilar to your problem).
Check it out to see if your motherboard is listed. Potentially you may have a hardware issue with bad capacitors.