Need a new graphics card

Ugh! Not much to work with really. Here's the motherboard and system specs for that system as listed by Dell:
http://support.dell.com/support/edocs/systems/dim3100/en/sm/specs0.htm#wp1052310

I believe you'll need to use the pci-e x1 slot for any decent graphics on that system. There's only two cards listed on newegg.com for that slot. And they're a little more expensive than I thought. And they're both ATi cards, not nVidia.
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010380048%201069620108&name=PCI%20Express%20x1

You'd certainly be better off spending just a tad bit more and getting a new system from directron.com. I know you're thinking it's too expensive, but these days it's not. And from the looks of that Dell you got, you could use a serious upgrade. Check out the stuff Directron has and you'll see why it's better to go new than to upgrade old systems.
http://www.directron.com/ho.html
Just don't forget to add the cost of an operating system and you'll be good to go.

GeForce 6200, plays TF2, so I am good to go. Thanks!!