my computer has a 160gb harddrive with 512 secondary memory ,1272mb usable memory and a 260gig pentium 4 processor. I'm using Nvidia 8400 gs PCI and its a piece of crap the only game I play is microsoft flight sim 2004
More aboutneed video card please
I would recommend a complete rebuild. Reason being is that if you get a new graphics card then the rest of your PC will hold back the performance of the new card.
There are no upgrade paths for your computer without a new processor and motheerboard. You wont find any more performance with a PCI slot.