poor gfx performance

[BigRoger]

i have a bfg 7800GT 256mb and when i play games i get really poor perfornance. When i play css i get 37-25 fps with everything on high and on dod s i got anywhere in between 40-15 fps everything on low.
Ihave tryed updating drivers and all that but i cant figure out what the problem is can anyone help.

 

[BigRoger]

just ran 3dmakr 06 and got 2992 and i usually just have msn and xfire runnign in the background and i have sp2 on.

 

[BigRoger]

amd socket939 san diego 3700
asus a8n-sli
Corsair 2GB DDR Value Select PC3200
anything else?

 

[BigRoger]

just the heatsink and fan what came with cpu and and 2 fans at back of case and one on the side.
psu is hyper 480w.

 

[BigRoger]

i have put the gfx power cable in and updated both mobo and gfx drivers i cant think what the problem might be