I purchased a used Intel core duo quad Q6600 to replace a E2220 dual core in a HP a6807c tower. PC has a IPIBL-LB mobo and HP support states this CPU is supported. Once installed I got BSOD intermitantly. I tried swapping out PSU so that is good. I tried HP support with their ideas, no good. I cleared CMOS, ran stress tests on CPU and RAM and they all passed. Original OS on PC was Vista 64 which was upgraded to Windows 7 64 while old CPU was installed about 8 months ago. Tried repair install with Windows 7 upgrade disk and I got BSOD or PC froze at about same time (5 minutes into install). When I put old CPU back in PC seemed to work fine. Already tried updating BIOS. No good. Do you think I have to do a clean install or is the CPU bad. I'm just about out of options other than exchanging CPU and hoping for the best.