Low FPS on a good PC

[jet399]

Hello guys,
When i play gran turismo 4 everything is fine, fps stays around 50 the hole time. But when i load up need for speed underground 2, i get past the menu where i load up my save, and after that my fps drops to 30 and the game runs in slow motion. Can anyone help me please?
Specs: 
i5 2500k
AMD XFX HD 7970
P8Z77

[refraction]

I believe enabling the hw hacks on gsdx and then under the hacks section setting skipdraw to 1 greatly helps the speed.

[jet399]

I believe enabling the hw hacks on gsdx and then under the hacks section setting skipdraw to 1 greatly helps the speed.

So my fps went up to around 35 now, but it still runs in slow motion :l