The announcement means Microsoft will meet — just barely — its revised goal of putting Vista in consumers' hands in the first month of 2007.
Windows Vista's code was released midmorning Wednesday to manufacturing — a step that allows the company to begin making the copies that will be distributed with PCs and sold at stores, said Jim Allchin, co-president of the Microsoft division that includes Windows, in a conference.
"This is a good day," Allchin said.
Microsoft had previously said it would release Vista to big business clients at an event at the Nasdaq Stock Market on Nov. 30, and Allchin reiterated Wednesday that corporations who buy Windows licenses in bulk will get the new system this month.
That's also in keeping with the company's revised release schedule.
The release will be the first major upgrade in more than five years to the operating system that powers most of the world's personal computers.
Vista boasts improved graphics, more effective tools for finding documents, pictures and other items on personal computers, and a new Internet browser, among other changes.
The software has been plagued by delays, the most recent of which was blamed in part on efforts to improve security. Microsoft products are a near-constant target of Internet attackers, and the company is often in the uncomfortable position of having to plug holes in its products.
Allchin cautioned that Vista will still face some security threats because attackers are growing more sophisticated. But he said a rigorous testing process and changes that make it harder for attacks to jump from one Vista-powered computer to the next should reduce those problems.
In its quest to get Vista out the door, Redmond-based Microsoft also has had to scale back some of its original goals, including scrapping a more sophisticated method for sorting and organizing data.
Analysts have said that scaling back the system could hurt the company if people don't see enough reason to upgrade.
The most recent delays also forced Microsoft to miss the holiday season, potentially dealing a blow to computer makers and retailers who may have been hoping for the new system to boost gift sales.
Microsoft and computer manufacturers are offering holiday shoppers coupons good for a free or discounted Vista upgrade.
It's not clear how quickly big businesses will start using Vista. It can often take months if not years for companies to test a new operating system and make sure it will work well with the other programs they rely on.
Allchin said Microsoft is providing tools that allow companies to test for compatibility problems more quickly than with past Windows releases. He also said he hopes the security improvements would drive companies to upgrade faster.
Microsoft shares rose 3 cents to close at $28.98 Wednesday on the Nasdaq Stock Market.