Acer Veriton 7900 Q6600 Refurb @ Acer $899
Its a refurb but will no doubt be covered by an Acer warranty. Its a Core 2 Quad 2.4Gz processor with 2 gig of RAM and a 320 drive. Comes with XP Pro.
They're marginally old stock in system terms but practically its still a good workhorse sort of machine.
Harris as an example still sell them for 1200 or so.
The site has a session or frames or something so when you go there click on the Acer Factory Outlet link and you'll get this machine.