Whenever I play, I get 20-30 minutes in and then *FREEZE!*

Fallout 3 has stopped working...
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It's not heating problem, I can run the game smoothly on medium settings. I don't see any problem here, help?

Post a dxdiag.
XP: Go to Start->run, type “dxdiag” and hit enter. Click the Save All Information button near the bottom right. This will save a Dxdiag.txt in C:\ by default. Then open the dxdiag.txt and copy/paste the information into your post.

VISTA/Windows 7: Go to Start->Search, type “dxdiag” and hit enter, click the Save All Information button near the bottom right. This will save a Dxdiag.txt in C:\ by default. Then open the dxdiag.txt and copy/paste the information into your post.