Microsoft renamed its free online storage service Thursday as Windows Live Skydrive, and relaunched it with several interface tweaks as a beta preview open to anyone.

Formerly called Windows Live Folders -- the name under which it briefly made a public appearance in mid-May before vanishing again into invite-only testing -- the service requires users to log in with a Windows Live ID. Most people are familiar with Live ID from accessing Hotmail, now called Windows Live Mail, or using Windows Live Messenger for IM.

Skydrive's storage allowance is 500MB; it lets users create and designate folders as private, public, or public-but-invite-required; and can be accessed using either Internet Explorer (IE) or Firefox. New features or enhancements that debuted in the refresh include image thumbnails and file uploading using drag-and-drop. The latter, however, relies on an ActiveX control, and so can be done only when using IE when accessing Skydrive.

Not a backup service -- it lacks the tools to automate file transfer from local PC to offsite server that, say, Mozy provides -- Skydrive limits individual uploaded files to 50MB or less. Currently, the best is restricted to users in the U.S., the U.K, and India.

Windows Live Skydrive can be found here.

Although long rumored to have a similar project in the works, Google has not yet released an "in-the-cloud" storage service -- which has been tagged with the moniker Gdrive -- or even publicly acknowledged one is in testing.