Which graphics card is best for G41

What CPU are you running? What size screen resolution? And possibly a price range? You have a PCIE slot so anything from a lowly 5450 to a high end 5970 will fit.

I am using C2Quad, with 4 gb ram and 20" inch monitor samsung, 550 watt PSU, i have PCI 1.0 express card slot and screen resolution of around 1940*900 i am not sure about resolution but it is the minimal supported by the motherboard.i am to see good at this resolution so if you can possibly help let me know difference between 9800Gt or raedon cards, which will fit better

Okay, i think HD5770 will be perfect for your need.  
And 5770 is faster than 9800GT.

Anyone have another suggestion?

ATI Rdeon HD 6990