NeweggFlash offers the refurbished HP Compaq 6000 Pro Intel Dual Core 2.6GHz Small-Form Factor Desktop PC, model no. AT492AV, for $49.99 with free shipping. That's the lowest total price we could find by $45 and one of the cheapest desktops we've seen (and the cheapest we've seen with Windows 7 Pro). Features include an Intel Pentium Dual Core E5300 2.6GHz processor, 2GB RAM, 160GB hard drive, DVD burner, and Windows 7 Professional. Deal ends December 1.
Note: A 90-day warranty applies, but it's unclear who provides it.