Gmod Very bad lag

I get 5-1 fps after 10 minutes and it lasts 4 hours. I need a master fix that can fix it for sure so that the game is playable. Here are my specs: Processor AMD athlon II X4 630 2.80 Ghz Installed memory, RAM 6.00 gb {5.75 usable} 64 bit OS windows 7 Nvidia Geforce 9100. I cant get a new computer or update my drivers, so dont tell me that.

Verifying Game Cache Files