How's this?
$474.00
OptiPlex GX280 P4-2800
Windows® XP Home
40 G (I) 7200RPM
512 Ram
CDRW
DVI (Digital) Adapter Card
Small Mini Tower
That is an awful lot of computer for less than $500.
The Optiplex line is generally intended for business, rather than home use, but in reality there isn't a whole lot of difference. I'd bump up the RAM, but maybe that's just me.