if you have time to wait around on websites like yugster.com
They have deal-a-day offers where items will sell for usually more than half off.

I looked at the past deals over the last months and basically a Dell GX computer of specs(2.8Ghz, 2GB ram, and like a 250GB HD or so with dvd/rom and maybe even a webcam with WINXP) will show up about every 20 days or so for only like $200.  Now you could get that and then go on newegg or someother site and buy a decent graphics card(9800GT?) for like $100.

Looking at it  now...in about 10 days another computer might come up?

But you never know

hers some of the recent deals
you can also look at previous months etc,
http://www.yugster.com/dspsitemap.aspx?m=12&y=2010