Is this overheating?

[wright_91]

I think my computer is overheating, but I'm not sure. In games, after about 10 minutes, the screen goes blank, saying 'no signal'.

The reason I think it's overheating is beacuse when I put a normal, domestic house-fan next to my computer, blowing air into the side of my computer, games last at least 40 minutes, sometimes even a hour or two before the screen goes blank. However, it depends on the game, as to how long they last.

I've ran Prime95 for a couple of hours, and there were no problems, so I think I've isolated the CPU. A friend suggested it could be my graphics card overheating. Any suggestions?

 

[wright_91]

My computer's quite old, but should still play games such as Medieval II total war and similar- which it does, until 10 minutes is up. GPU: Radeon X550 256 mb. CPU: Pentium 4 630 - which I know had heat problems. Also, I've got a media centre type case, so it's small, which I completely regret now. My computer's prebuilt, so I don't know what the PSU is, and I can't open my case to have a look, because it seems to be stuck.