Games hang and monitor says no signal

I tried running Team Fortress 2 in a windows with Everest showing temperatures. CPU+cores keep around 65C and my videocard around 60C. They're the only things that increase in temperature (CPU is around 45C when idle and videocard 50C). I'm really wondering if I should bring it to a repair shop, but what are they going to do? Play games untill the error shows?

Edit: I also did the Power Supply Calculator. I'm not sure about my CPU though, since there are 2 models, a G0 and B3. With the G0 I get 463 Watt and with the B3 I get 494 Watt. So my 420 Watt PSU doesn't seem to be sufficient (which is surprising, because I had it build by a shop and I'm guessing they would know what kind of PSU it needs). I don't have a lot of experience with this, so my question, is it possible that I would actually need 494/463 Watt? Wouldn't I have noticed it before then? And is it possible this is the cause of my problem?

 

Well, this morning I brought my computer to the workshop. They told me it should be done today or maybe tomorrow and the fact that they haven't called yet is telling me they probably don't have a clue either.

 

Yeah, I think I'd be able to fix it better in person as well, since I could actually test it (and I have no idea how the shop is going to determine what's wrong without playing games all the time and seeing if it'll freeze ) but I don't have the spare hardware lying around to switch, so I could either buy a lot of new hardware untill I found the piece that's not working or get it to the shop..

 

Well I just got my computer back. They replaced the motherboard which was apparently malfunctioning. I'll go test it now and see if it works.

Edit: No! The problem remains! Thank god I still had waranty so I didn't have to pay. Conclusion: it's not the motherboard. I found my GeForce 7900 yesterday and I'll switch to that later to see if that's causing the problem. Also, I seem to have taken the wrong processor with the PSU calculation, and apparently it's 253 (for the B3) or 245 (for the G0) so I might switch to a 300 watt PSU I have lying around to see if that works. If not... then there's really nothing left to check..

Edit2: Switched videocard --> problem solved..

 

Your Geforce 7900 will play UT2004 perfectly If you have warranty on your old graphics card get it replaced or a refund. As of now I have a Sapphire ATI 4870 Toxic edition GFX card and have had no problems running any games on it so far (touch wood).

 

I called the shop to see if I could trade my GeForce 9600 for another one but they didn't have it in stock so I'll have to wait for that, so for now I'm using my 7900. But yes, I can finally play UT2004 now! Played it a bit this afternoon and liked it a lot. Be sure to let me know when the Digiex crew joins up for a game!