Weird freeze/sound loop when playing certain games

[Lemon Jelly]

need a little tech support. For some reason when I play games after about 10 mins it freezes and this loud sound comes from the speakers. hell I have no idea what it could be. At first I thought it was my GPU overheating (even with the fan on at 75%) but the weird thing is I can play TF2 fine for hours and nothing happens but got the freeze when I was playing Quake live?!?
heres a video of it happen when I was playing COD4
http://www.youtube.com/watch?v=Api6Bur8YRw

 

[mister g]

I would try reinstalling the game, but since you come here often I think you already did that. Do you have a sound card? Otherwise list your PC's specs.

 

[Lemon Jelly]

Its not just one game but a couple and no I don't have a soundcard. It's weird because I use to be able to play these games fine without any freeze's, It just started happen recently.
Mobo: Gigabyte GA-EP45-UD3P
CPU: quad core q6600 2.4GHz (not overclocked)
Ram: 8gigs of kingston DDR2 800
GPU: XFX 4890
PSU: PC Power & Cooling 610W

 

[mister g]

I would get a can of compressed air and see if I could clear out dust on the fans and heatsink for PC, heat may or may not be a problem that's what I'm saying.

 

[gothicfighter]

I have the exact same problem. Sometimes I play CoD MW2 for like 2 hours and then the game simply freezes and a sound loops really fast. I can only hard reboot. I think it's from the Video Card(after reading lots of thread in which ati users reported the same problem). It has also happened one in Assassin's Creed.