possible gfx card problem!

Hi, could really do with some help please, what it is i recently upgraded my system, new mobo, new gfx card, more ram, and since i put in the new gfx card (Old one was an nvidia gt 240 512mb) GTA IV played perfectly but now i`m getting about 8 fps and its unplayable, i can play battlefield 3, max payne 3, mass effect 3 etc with no problem at all....

my specs are...

Mobo - Asus m5a 78l-m
Gfx - geforce GTX 560 (1gb) directcu
Mem - 8 gb DDR3
CPU - AMD FX-4100 quad core 3.60 ghz
OS - Windows 7 home premium

The latest drivers are installed, any help would be very much appreciated

Have you adjusted the settings while in-game, under video? Sometimes it takes that adjust in the game itself to tweak the GPU to it's full potential.

thanks for the reply, yes i have altered the settings but made little or no difference it was still jerky but i`ll have another go in a bit

well, altered the settings once again, ran the benchmark test and was getting an astonishing 13.87 fps, thats pathetic!!!