Last week my PC went belly up. The PSU cut out and wouldn't come back on. I replaced it with a new 500w PSU hoping that would solve the problem but it didn't unfortunately. It would power the mobo (CPU fan spun, power switch worked for on/off) but do nothing else. Guessing that the PSU going took out the mobo/cpu I bought new ones. They arrived today but after installing couldn't get them to work either! lol They had the exact same problem that my old mobo/cpu had. As a test I decided to install the old mobo/cpu in another case with the 500w PSU and lo and behold they came to life! Guessing that there was some kind of problem with my other case (although I'm still confused as to how that's even possible! lol) I moved the new mobo/cpu into the other case but still had no luck. As a test I removed the ram and switched the PC but wasn't greeted with the usual error beeps. The new mobo is a Biostar A780L3L 760G, the new CPU is an Athlon x2 250 and I bought new DDR3 RAM as the board doesn't handle my old DDR2. All I get on boot is a black screen, it never reaches the BIOS/post stage and like I say there's no error beeps if I try booting with no ram installed. My old board is a Biostar GF8100 m2g+ which has an AM2+ socket and claims to be compatible with the new CPU. I updated the BIOS as the Biostar website stated and stuck the AM3 chip in it but still no joy. It powers up, then after a few seconds powers down again, then a few seconds later powers up again and repeats this cycle til I switch it off. The power switch works to switch it off when it's in this loop as well. Anyone got any ideas or am I right in thinking that the CPU is DOA?