Windows 7: my computer slows down every 10 min for 2 min when i play game

hi guys. i have a problem , my computer detail :

win xp 32bit
graphic card: ati radeon hd 5870 1gb
ram: 4 gb
cpu: amd athlon 64 x2 dual core processor 6000+ 3.00 ghz

plzz help. when i start any game it goes fine at the begining and after 5 or 10 min of playing it slows down for maybe 2 min and again works fine and again same thing. how can i fix this? i am going to change my win maybe it helps?

Heat problem? Old or corrupt drivers? old hard drive about to give out? perhaps if you give us a few more details we can try to give you more help?

wait a sec... sounds like a heat problem to me.... something gets too hot, so it underclocks (or alternatively the fan was too slow to actively cool, until it started to spin-up because of the heat), then it cools down and you can play normally again...

What is the Game? Do you have the System Requirements to Run that Game?

Josh