Currently I have an AMD 1600+ in my system and recently upgraded to a 2600+ 266 FSB. After installing the latest BIOS from Epox and stripping my system down to just the MB, CPU, RAM, Video and HD, I still get the Blue Screen Of Death

that says ***System Has Halted Hardware Malfunction*** Just after the XP Pro logon screen appears. I've cleared the CMOS, tried the last 3 BIOS versions, even in Fail-Safe Mode. Get the same thing.
I returned the CPU and bought an AMD 2400+ 266 FSB T-Bred. I still get the same thing. Epox support tells me that the 2400+ and 2600+ work fine. How can this be, what am I doing wrong? I read several posts concerning similar issues, but I still can't get my system running.
FYI... When I put the 1600+ back in, everything works fine.
See my Sig for my system stats.
Thanks for any help.