Buying Video Card

[squallss4]

Hey guys Im new into this video cards thing, well I have an old system:

2.6GHz AMD Athlon 64 X2 dual-core processor 5000+
4GB PC2-5300 DDR2
500GB hard drive
NVIDIA GeForce 8200 graphics high-definition

I want to buy a new video card but I don't understand which I should buy, I was hoping you guys can give me a tip or two, thanks

 

[neon neophyte]

depending if you are doing this for specific games, you may want to have an ati/nvidia bias.