[bluck2008]

Hi, anyone. it would be super if you could help or at least let me know what you think could be the problem here, as its giving me a huge headache

in short, this is what has happened since i bought this PC:

1 - PC functioned perfectly (edit: with particular programs open, monitor would lose signal after between 1 and 10 minutes and would have to reboot, and would be fine again. PKR, WoW, Call of Duty would all make the monitor cut out randomly. Games such as Counter Strike Source never gave me a single problem)
2 - turn pc on the next day, no signal
3 - tried other monitors, same result. also tried re-seating the graphics card.
4 - left the pc alone for months
5 - tried it again today, and it worked, showing no errors and running games perfectly (i was getting 240fps on source)
6 - turned it off
7 - turned it on, getting no signal again

I thought something within the PC must have broken at first, but then with it working today..surely it cant be? 240fps on source surely means the graphics card is ok? another thing i noticed is whenever it has worked in the past, it has always displayed a message at the beginning of booting, which is something like "error, disk not found!!".

Anything that could help me out would be hugely appreciated. i bought this pc about a year ago and have only managed to get about 40 hours of use out of it. thank you.