Here's my crazy story when I went and upgraded my CPU.
Very recently I swapped out my 2100+ for a 2500+ Barton. I had one hell of a time getting the thing stable because I failed to realise my older bios version did NOT support Bartons!!!
Every reboot ended with the "siren" telling me something was up.
I had to hit my insert key to clear the bios. OK. Made my changes to the bios setup. Reboot. Siren again!
Because I had to hit the insert key every time I wanted to boot into Windows it would also disable EVERYTHING on the mobo. No floppy... no USB.... no NIC.... no nothing.
So, I pulled down the latest and greatest Bios from Epox (on my other PC) and I had to burn the darn thing on a CD. Remember, no floppy.
Had to flash while I was still in XP using winflash utility. Flash worked great!
Went into the bios hit the "Load Optimised Defaults" and hit "save changes"... rebooted.
SUCCESS!!! It finally recognized the CPU as a 2500.
I have since upped it to 3200+ specs with just a slight bump in the CPU Voltage. Stable as a rock.
I am running Mushkin DDR3200 "222" RAM. REALLY awesome stuff.