Random pc shutdown

[NeedMoarFarms]

I cleaned out my computer today with a can of compressed air and now it's all nice and clean. However, I've had a few random shutdowns which has never happened before. I played TF2 for an hour and it was fine. But then half an hour later when the computer had been sitting doing nothing it randomly shut down, not a reboot, just shutdown. My temps seem absolutely fine (actually a little lower now since my case is dust free) and I'm certain I never touched anything in the case since I kept the nozzle a good 10cm away from all the components, so I really doubt it's an overheating problem.
The shutdowns have happened a few times, if this keeps happening should I test to see if there's a problem with my power supply?

[Zsev]

Thats really weird... surviving 1 hour of TF2 but shut downs while idling in windows.
Perhaps try to reseat all your components again just to check their connection, then do a chkdsk to test for bad sectors.

[NeedMoarFarms]

Hmm, hasn't done it in over 6 hours, dunno what caused the shutdowns then :S .

[XA04]

May I suggest a virus scan? (e.g. http://housecall.trendmicro.com )

Not certain what it could be.. my first guess would be temperature also.. but as it happens whilst idling within windows it could be a virus I suppose. If it happens again then maybe try playing with a Ubuntu live cd for a couple of hours and see?

[NeedMoarFarms]

Well it hasn't happened since. Did a virus scan earlier today and found nothing.

Ah well, as long as it doesn't happen again I guess I shouldn't worry about it, thanks anyway.

[zarn]

Any power connections loose e.g. a fan? Maybe you blew dust into the fins of a heatsink? Sounds like overheating

[TAKTAK]

i'd put money on your HSF not being installed accurately and not applying pressure to the cpu, in which case, a slight knock with an implement (say a chair) would cause the cooler to fall off completely

[NeedMoarFarms]

i'd put money on your HSF not being installed accurately and not applying pressure to the cpu, in which case, a slight knock with an implement (say a chair) would cause the cooler to fall off completely

someone get this man a cookie!

bravo, bravo .