Low Frame Rate In Some Games

Well i got low FPS even though i passed the recommended system requirement.This is some of the example

GTA SA Highest - 11-8
GTA SA Medium - 13-15
GTA SA Lowest - 20-15

Oblivion Highest - 11-9
Oblivion Medium - 16-10
Oblivion Lowest - 20-15

My Specs
Geforce 8600GT 256 MB
2 Gb ram DDR2
Intel Pentium D CPU 2.66GHz (2 CPUS)

So is it really my specs thats not enough or was it something else?it'll be greatly appreciated if someone could help me with this

If I'm not mistaken, your right you should be getting much higher frames. Turn off any background programs (AntiVirus, AntiSpyware, etc.). If that doesn't work, update the Graphics card driver here: http://www.nvidia.com/Download/index.aspx?lang=en-us

Then download the latest game patches. You can usually find them on the official websites.

Tried that still didn't work

Just so you know, having a dual core processor doesn't mean you have 2 processors. It means it splits up the ghz to increase speed. FYI.

Also, I am already kinda stumped. Make sure your not overheating or anything. Use a can of compressed air or something similar to blow the case out...