i cant get up the fps i´m stuck @ 26-40 fps on sigel wow..

setup:
motherboard: Gigabyte GA-MA770 AM2+
CPU: Amd athlon 64 x2 6000+ 3,1 Ghz
Ram: 4Gb
Graphic Card: Winfast PX 9500 GT (Nvidia) (512mb)
Os: Windows Vista

My old one was realy old and only 256mb graphic card and the fps was 50+ always.. the fps was down to 20 with 3 wow up @ the same time..

someone know what to do????