Microsoft will put Windows 7 on store shelves and computer makers will have systems ready to sell with Vista's successor on October 22, the company confirmed today.

Microsoft will also offer discounted or free upgrades to Windows 7 to users who buy PCs in the months leading up to the operating system's launch in a program dubbed 'Windows Upgrade Option', a company spokeswoman said Tuesday. Although the name is new, the program had been reported as early as January, when a usually-reliable Web site leaked information about the deal, including its July 1 kick-off.

Until today, Microsoft had been coy about naming a release date for Windows 7, although it edged toward a timetable last month. Both Bill Veghte, the senior vice president who runs the Windows Business unit, and Steven Sinofsky, the senior vice president of the Windows engineering group, said then that Windows 7 was on track for the holiday selling season, and would make the final milestone -- called "release to manufacturing," or RTM -- in mid-August. Today, however, other company spokespersons said Microsoft is shooting for RTM by the end of July.

Details on the Windows Upgrade Option were not immediately available, but analysts have assumed that it would resemble Vista Express Upgrade, a program that gave people who purchased Windows XP PCs between Oct. 26, 2006, and March 15, 2007, free or inexpensive upgrades to Vista.

Vendors were allowed to set the price, if any, of the XP-to-Vista upgrades, and it's believed that they will have the same flexibility for Windows 7.

This isn't the first time that October has been named as the likely ship date for Microsoft's new OS. In an interview last month, an Acer executive based here in the UK said "October 23 is the date that Windows 7 will be available." The executive, Bobby Watkins, the managing director of Acer's U.K. operations, also confirmed that customers who bought a Vista-powered computer from the company in the 30 days leading up to Oct. 23 would receive a free upgrade to Windows 7.