After several delays, it appears Microsoft may get the next version of its Windows client operating system to customers according to its current schedule.

The company on Friday made Windows Vista Release Candidate 1 available, which means the OS is in its final round of bug fixes and tweaks before it will be ready for release to the general public.

Windows Vista RC1 is available to TechBeta and Technology Adoption Program (TAP) program subscribers Friday, but MSDN (Microsoft Developer Network) and TechNet subscribers won't get the OS until next week, Microsoft said.

Microsoft has said since March that Vista will be available to business users in November and consumers in January 2006.

With the last major upgrade to Windows, Windows XP, it was about two months between RC1 and the product's release to manufacturing. If Vista follows a similar schedule, with RC1 out Friday, the release to manufacturing -- and a release to business customers -- could happen as soon as early November.

OEMs (original equipment manufacturers) typically need about six weeks to get the OS installed and tested on PCs before putting those machines on the market. If Windows Vista makes it to manufacturing by the end of November, it could hit its January release date for consumers.

Online retailer Amazon.com is already taking pre-orders for Vista, and has listed availability of the OS as January 30, 2007 on its Web site.

In a letter to TechBeta subscribers on Friday, Jim Allchin, Microsoft co-president of the Platforms and Services Group, thanked them for their support and feedback, and mentioned several improvements to the OS that have been made since Beta 2 was released in May.

"We’ve made some UI [user interface] adjustments, added more device drivers and enhanced performance," Allchin wrote in the letter. He added that Microsoft will continue to work on Vista's "application compatibility, as well as fit and finish" until its release to manufacturing, which is yet to be determined.

Allchin also advised ISVs (independent software vendors) to use RC1 to certify its applications to run on Windows Vista, and asked for more feedback from testers to improve the OS before its final release.

"Windows Vista is going to touch hundreds of millions of lives all around the world," he wrote. "Thanks for everything you’re doing to help us give them the best experience possible."

Allchin's letter is available on the Windows Vista team blog at http://blogs.technet.com/windowsvista/default.aspx