Newegg offers the refurbished HP 8100 i3 Dual 2.93GHz Desktop PC, model no. 8100 SFF, for $269.99. Apply coupon code "VISACHECKOUT" and checkout with Visa Checkout to drop the price to $249.99. With free shipping, that's $150 off and the second cheapest i3 desktop we've seen with 4GB RAM and 500GB hard drive. It features an Intel core i3-530 2.93GHz dual-core processor, 4GB RAM, 250GB hard drive, DVD burner, and Windows 7 Professional 64-Bit. Deal ends October 4.
A 90-day warranty applies, although it is unclear who supports it.
Update: Specs corrected.