Alright, so I've upgraded my power supply and my processor. PC Power & Cooling 350 / Thermaltake Silent Purepower 420 Athlon XP 2200+ / Athlon XP 2500+ I turn it on and everything is working. Bios reads Barton 2500+. Windows works fine, games work fine, prime95 torture test etc. So then I reboot to change some bios settings (I cleared the cmos before installing the new CPU). I change things around to the way I like and reboot... Nothing. It doesn't post and I don't hear any beeps. All of the fans are working but the CD-Rom won't open and the HD isn't spinning. So, I hit the reset button and it posts again. I go back to the bios, and even without changing anything it happens again. I can click "exit without saving" and it still happens. Like I said, when I'm in Windows things work perfectly. I was searching on here and I read something about the PSU not resetting when you exit the BIOS, so it thinks it doesn't have enough power (or something like that!), so when I reset manually (with the button) it works again. I have tried taking everything out of the PC except video, ram and HD and the problem persists. Thermaltake Purepower 420 ABIT KD7 Mobo Athlon XP Barton 2500+ (temps are fine) Kingston 512MB PC2700 DDR Maxtor 7200RPM 60GB Would appreciate any help, because this is driving me crazy! :)

Everything works fine in windows because the BIOS becomes a slave device once it hands over control to windows. You are correct in assuming this is a BIOS issue. I am thinking that one of your Busses is overclock. Most likely the PCI Bus. When that happens. You get data corruption. You don't want your PCI bus to excede 36 mghz, Preferable it should run at 33 mhz. Also. Your RAM speed should follow your FSB Speed. So if your FSB is 166 then your RAM speed should be 166. That's because the AMD processor is double pump. 166+166=332. Thus your FSB speed. Your AGP bus should be 1/2 of your FSB and your PCI divider hould be set to give you 33 mhz based on your FSB. Hope this helps.