Web users got an brief sneak peak at Microsoft's long-expected online backup service, once known as Live Drive, this weekend.

The hosted backup service, now called Window Live Folders, will initially offer users 500MB of free storage that they can organise into personal, shared and private folders to separate content and limit access. "Password-protected online file storage. Always available where you need it," the site's tagline read before Microsoft pulled it.

Microsoft said that the service, which has yet to enter beta testing, will be accessible to both Windows and Mac users via the Internet Explorer and Firefox browsers. It will be accessible through Windows Live ID (formerly Passport), Microsoft's single sign-on service, which it also uses for other Live offerings, including Hotmail and Messenger.

LiveSide.net first spotted the "live" Windows Live Folders and posted several screen shots of the service on a blog entry. There were no clues on the site regarding a desktop client for the web-based service, however, or whether it automatically synchronises local files with versions stored online.

In 2005, Microsoft acquired the FolderShare service from a Texas start-up. FolderShare, since folded into the Windows Live service line-up but not touted by Microsoft for months, lets users synchronise files on multiple machines. At one time, it was thought that Live Drive would integrate some of FolderShare's features.

Windows Live Folders, nee Live Drive, was first confirmed by Microsoft in April 2006, when the company's chief technology officer, Ray Ozzie, mentioned it in an interview with Fortune. Rival Google had accidentally spilled a few details of its own storage service, Gdrive, a month before.

Microsoft did not immediately respond to a request for additional information on Windows Live Folders.