New Computer Suggestions

I'm not computer savvy so some suggestions would be appreciated. There is a Pentium 4 computer I can have for cheap but don't know if that would be enough. It's an XP, has 1GB RAM and 160 HD. I'd have to get a graphics card but I don't know what kind of slot it has.

Other than that, what would Ii need? AMD or Intel dual cores? What kind of graphics card? I've done some research but am unsure about all the choices, especially since affording a dedicated gaming PC is out of my price range. I don't think I can spend more than $400 in the next couple of months. Any help is appreciated.

Thanks

Go for intel dual core if you can. Also, for the graphics cards I've never had any MS problems regarding graphics with a Mobile Intel Express chipset. Can't really help past that sadly D: