Pranksters have taken to posting what they claim are leaked builds of Microsoft's next OS, Windows 7, but which turn out to be, according to downloaders, just fake disk images full of nothing.

According to the Windows enthusiast site Neowin, several BitTorrent sites have been seeded with files posing as the M1 - for Milestone 1 - build of Windows 7, an early preview version of Windows Vista's successor meant for Microsoft's hardware partners. But downloaders commenting on Neowin, as well as those on BitTorrent sites such as Pirate Bay, have confirmed that the disk images are bogus.

"It's fake. I [downloaded] 10% and opened with a hex editor, just strings of [zeros]," said a Neowin commenter identified as "bjc4ever" Sunday.

Although searches using the string "Windows 7" at Pirate Bay initially brought up results, while Computerworld was examining the results and reading downloader comments, the site pulled the listing. One commenter, however, put it this way: "FAKE FAKE FAKE FAKE FAKE."

Interest in Windows 7 spiked last week when a poster to a Neowin forum leaked what he claimed were details of the new operating system and bloggers spread the story. Speculation has also been driven by the anonymous blogger authoring "Shipping Seven: Random thoughts from somebody working on the next Windows OS," primarily because the writer claims to be a Microsoft developer.