hey people i have a interesting problem

Load game Grey Screen so i thought could it be by resolutions. Tryed that got a screen but it was Huge . So i trying making smaller and it jammed up.
Every other game ive got works

So im thinking its a graphics card

Comp is updated to current patches, upgrades etc

Computer

AMD Athlon 64 x2 Dual
Core Processor 6000+3.25 GB of Ram
ATI Radeon HD 3800
Creative SB X-Fi
4 Hardrives 2.5TB