WinRumors reports that copies of a Milestone 3 Windows 8 build appeared on eBay recently.

Microsoft is currently working on pre-beta copies of Windows 8 in preparation for a beta release at the company’s BUILD developer conference in September. Recent reports suggest that the company reached build 8042 on July 7 and is planning to hit build 8100 for the beta stage. The software maker is also rumored to be preparing a pre-release build of Windows 8 at the Worldwide Partner Conference this week. It’s unlikely that the company will issue a build but it will talk more about Windows 8 and possibly share a second “building Windows 8″ video. Microsoft first introduced Windows 8 at the D9 conference in early June. The company made an initial “Building Windows 8 video #1″ available as part of a series of videos that will be released as the BUILD conference draws closer.

  Windows 8 builds on sale at eBay auction site