Microsoft will turn off the download spigot for Windows 7 Release Candidate (RC) on Thursday around 11 a.m. ET, the company confirmed on Tuesday.

The company has been sending out e-mails to users who have already downloaded the release candidate, reminding them of the impending deadline.

On Monday, a company spokesman repeated the warning, while a spokeswoman today said that the tap would be closed Thursday morning.

Microsoft first offered Windows 7 RC late on May 4, saying then that it would provide a download through at least July.

Late in June, however, the company said that it would allow downloads until Aug. 15, then last month quietly extended that deadline by another five days.

Citing company policy, a spokeswoman today declined to specify how many copies of the RC have been downloaded since early May, although she said it was "in the millions."

Although the actual downloads will not be available after Thursday, users who have obtained the disk image file may still request a product activation key after that date, Microsoft has said.

Other users, notably IT professionals and developers who subscribe to the TechNet and Microsoft Developer Network (MSDN) services, have already moved on to Windows 7 RTM (release to manufacturing), the final version of the new operating system. Those users have been able to grab copies of the English RTM since Aug. 6.

Windows 7 RC is set to expire March 1, 2010, at which time it will begin to automatically shut down at two-hour intervals. The RC expires on June 1, 2010; after that date, it simply won't boot.

Microsoft has slated Oct. 22 as the on-sale date for new PCs packing Windows 7, as well as for retail copies of upgrades to the operating system. Prior to that date, one of the few ways to obtain a legal, final copy of Windows 7 is to attend one of the 25 launch events Microsoft is hosting in the U.S.

Those events begin Sept. 24 in Denver, Miami and Minneapolis, and end Nov. 9 in Baltimore, Houston and St. Louis.

A complete list of the sites and schedule is available on Microsoft's site.

Until Thursday morning, Windows 7 can be downloaded in 32- and 64-bit versions, and in English, French, German, Japanese and Spanish editions, from this site.