My second pc has been playing up on and off for some time now, some months ago it would often start up on its own, maybe boot all the way to the desktop or just stay on for a few seconds and then turn off again. I initially tried a new PSU but without success, I checked all connections and reseated memory and cards but still the same issues, eventually I swapped the mobo which appeared to have cured the problem. It worked for over 9 months and has recently started the same problem again, annoyingly often in the middle of the night. I came to use it today and it wont boot up at all, no POST nothing, no beeps from the mobo. I again reseated everything, tried a new PSU but no success. I can't say that this machine works hard because I only switch it on occasionally, often just to update the software and check its working OK. I think I used a couple of weeks ago and it was fine. At this point in time I am a little baffled and am hoping you guys can come up with some words of wisdom.