Help! Just upgraded getting low FPS in any game

Hello, I just built a new computer....

EVGA 896-P3-1255-AR GeForce GTX 260 Core 216 896MB 448-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail

G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Dual Channel Kit Desktop Memory Model F3-10666CL8D-4GBHK - Retail

GIGABYTE GA-MA790XT-UD4P AM3 DDR3 AMD 790X ATX AMD Motherboard - Retail

AMD Phenom II X4 945 Deneb 3.0GHz Socket AM3 125W Quad-Core Processor Model HDX945FBGIBOX - Retail


Everything seems to run fine, but whenever i play a game, it dips down to 10 to 20 FPS when something is moving around or lighting happens, its ridiculous

I'm running windows vista 64bit and i have the newest nvidia drivers.

I turned the graphics all the way down to low, played offline, and it still happens on left 4 dead.

I tried installing call of duty world at war and it took FOREVER so i canceled it assuming something is wrong with it moving so slow.

I have an amazing computer and it should be killing this game....any suggestions on how to narrow down my problem?