[Graphics Cards] DDR3 graphic cards on DDR2 Motherboard?

Yes, they will work.

Can you list want kind of graphic card that are compatible?

Yup it'll work. But, the performance may bottleneck so don't waste your money buying a high-end graphic card. Get the GTX 550 Ti. I use that on my old PC (C2D 2.33Ghz, Intel DG33fb DDR2 mobo) and it works great! You won't need anything else.  

HD 6670 or HD 7750

well please dont go for hd7000 series graphic card from amd.. there is no guarantee it would work on your older pcie 1.1 .. amd has altered their power delivery system for hd7000 series card so that they consume less power but in turn sacrificing compatibility with pcie 1.1 and 2.0. ok with now that being said you havent specificed what games you wanna play and at what resolution.. please specify that first then we can recommend you some cards

ok this is the link if you guys dont believe me about hd7000 series cards not working in older pcie 1.1 and 2.0 based mobos
http://www.overclock.net/a/the-final-answer-to-the-cont...

ok as far ddr3 graphics card is concerned yes it will work in your pc ..even ddr5 will work.. coz ddr3 and ddr5 of graphics cards is different and has nothing to do with the ram type  

Thank you guys for the reply  

A

Upgrade because i wanna play Battlefield 3 smoothly and the resolution? umm HD? ._. At least the graphic card can handle BF3 very smooth with High graphic.  

GTX? The price are bit expensive for me  . Other graphic card that are cheaper than GTX?

Yes, GDDR and DDR are two totally different things.

It will be bottlenecked by whatever CPU you have.

Nvidia GT 430 and GT 440 should work on old motherboards.