[Johnj]

For a low cost box that is upgradable try PowerSpec at Microcenter. The 4985 has an Athlon 2.4Ghz processor, 256K L2 Cache,256MB 2100 DDR RAM, 32MB Pro Savage AGP Shared video, 40GB ATA HD, 1.44 Floppy, 52X32X52 CDRW, Intergrated AC97 Audio, 1 open (4X) APG/3 PC!, and Windows XP Home for $450.00. Comes with an ok keyboard, crappy mouse, and no monitor.
Add a video card ($50-$400) and a decent mouse ($32-$100)

Of course this would be better with a 8X APG slot, but we are talking buget here.