I had to test my CPU (P4 3.2GHz 800Mhz FSB Prescott) in my parents' computer because my own motherboard quit on me and I needed to make sure that my CPU was ok, so I removed their CPU (P4 3.0GHz - I think it's a Prescott as well, but their mboard (ASROCK P4V88) is compatible with both, so it shouldn't make too much difference) and replaced it with mine. The computer powered on, POST-ed, and everything seemed to be fine, so I was relieved that my CPU appeared to be working properly.
The problem - I took out my CPU and put theirs back in, and now their computer won't POST. It powers on, the fans spin and all that, but the screen stays blank and there are no beeps.
I tried replacing the video card and connecting it to a different monitor to be sure that wasn't the problem. I also reseated the RAM, replaced the RAM, cleared the CMOS, and even tried another CPU (a celeron 2.4GHz that I had laying around), but there was no effect.
Is it possible that my CPU was damaged even though it appeared to be working? Is it possible that my CPU damaged their motherboard? Is there anything I can do?