Newegg offers the refurbished Dell Optiplex 780 Intel Core 2 Duo 2.9GHz Desktop PC, model no. DTDEOP780-SFF2W, for $179.99 with free shipping. That's $31 under the lowest total price we could find for a similarly-configured refurb Optiplex 780 with a smaller hard drive. Features include an Intel Core 2 Duo E7500 2.9GHz dual-core processor, 4GB RAM, 1TB hard drive, DVD-ROM, USB, and Windows 7 Professional.
A 1-year warranty applies, although it's unclear who backs it.