I know this is probably an old issue by now but ive recently built my own pc with the phenom x2 550 and the M4A79XTD EVO i know that you can unlock the 4 cores on this mobo as plenty of other people have so i decided id give it a try. i can get the 4 cores unlocked so that in the bios it says that it now has 4 cores but it wont load windows 7 64 bit im guessing that this means that the 2 other cores are defective but i just want to make sure this is the case before i give up on it
I had the same difficulty. That means one of your cores is bad. Your BIOS may allow you to unlock one of the extra core manually. I tried that on my Gigabyte board and found out that my 3rd core was bad, but the 4th core booted into windows and is fully stable after a prime95 torture test.