hmm, yeah i guess i can get a decent 450W PSU for like $20. Well, I checked CPUZ and I couldn't find where it said if I had a PCI Express x16 slot. However at the dell specs page for my computer :
Vostro 200 Slim Tower
The page says that my computer has a PCI Express x16 slot. Its pretty new, it should come with one. If it helps, the motherboard is a Dell Inc. 0CU409. I googled for it, but couldn't really find any specs on it.
Yeah, I have a e2140. I don't really know how to overclock it, but its not like I don't know what overclocking is. And yes, my computer is pre-built. It was cheap though!
So, I'm probably going for a XFX 7900:
XFX GeForce 7900 GS Extreme Edition 256MB GDDR3 SLI PCI Express Dual DVI HDTV Video Card PVT71PUDE3 at TigerDirect.com
and also a 450W PSU:
Power Up 450-Watt ATX 120mm Fan SATA-Ready PCI-E-Ready 24-Pin Power Supply GEN-2005 at TigerDirect.com
not sure about this PSU: is it made by a good manufacturer?
Thanks for all your replies!