Microsoft has completed Windows 7, reaching a landmark moment in its efforts to revive its flagship PC operating system.

The company this afternoon announced that it has released Windows 7 to manufacturing. The milestone, commonly abbreviated as "RTM,"  means the company has finished the development process and dispatched the operating system to be put onto installation discs and pre-installed on computers. For the record, the build number chosen as the final version was 7600.16385.

Microsoft CEO Steve Ballmer was slated to announce the news this afternoon at the company's internal MGX sales convention in Atlanta. Neowin has photos and details from MGX, culled from employees posting about the event on Twitter and other sites.

In addition, the company today announced that it has finished Windows Server 2008 R2, a major update for its server operating system.

Windows 7 is slated for public release Oct. 22. The company has gone to great lengths to try to avoid the compatibility problems that hampered the January 2007 debut of its predecessor, Windows Vista. The previous operating system suffered repeated delays. The Windows 7 development process, under newly minted Windows President Steven Sinofksy, has been much smoother.

ZDNet's Mary Jo Foley reports that there will be "a bunch of new hardware that has yet to be seen from a variety of manufacturers that will be preloaded with Windows 7" on the Oct. 22 release day. Microsoft is hoping that PC makers and other tech companies will capitalize on Windows 7's new features, including touch-screen technologies.

Other new features in Windows 7 include simplified home networking, an overhauled taskbar, and the ability to snap open windows against the side of the screen to quickly resize them.

Microsoft announced pricing for the different Windows 7 versions last month, offering Windows 7 Home Premium for $40 less than the comparable Windows Vista versions. The company yesterday also confirmed that it will offer a Windows 7 Family Pack, for installing the operating system on up to three computers, but it didn't announce the expected pricing for that package.

The RTM announcement comes a day before Microsoft reports its fiscal year-end and fourth-quarter financial results.