I just recently swapped my AMD Athlon 4200+ 2.2Ghz dual core for an AMD Phenom II 940 deneb 3.0Ghz quad core. After the INSTALL mobo found it fine. I had checked before I bought for compatability. I have a M3A78-CM mobo with 3Gig 667Mhz. As Windows Vista Ultimate sp2 started it was fine. After booting fully, certain services would suddenly stop. Sidebar closed several times. If I tried ANYTHING heavy duty like media center, BSOD. I ended up putting the original back in. No problems. Problem is I went through this about a year ago when I tried putting in an AMD phenom X4 9600 2.3 Ghz. I had the identical problems before, yet I pursued it then. I had reimaged windows, updated mobo firmware, PULLED my hair out. It got so bad Windows woudnt even get to logon page before BSOD. I had researched and found out about the TLB bug in the Phenom X4 9600. I figured it was a loss, so time went by, and here I am again with a processor (as far as I know) does not have the TLB problem. If there is anybody with any suggestions please help. I am about to give up and try and TAKE it somewhere (if theyll work on it). Any help would be greatly appreciated, any other info needed please let me know