Microsoft Store has the Lenovo IdeaCentre H520s - 2561 2nd Generation Core i5 Desktop (Glossy Black) for
$399 with free shipping. Includes keyboard and mouse. Features Intel Core i5-2320 3GHz processor, 4GB DDR3, 500GB HDD, 802.11b/g/n wireless, and Windows 7 HP x64 installed.
Newegg has the Lenovo K410 11681DU Core i5 8GB 2TB Desktop for $540 with free shipping