The company released RC1 to its TechBeta community of testers on Friday September 1, 2006, according to a memo published on Microsoft blogs.

The operating system is in great shape with RC1, but there’s still a lot of testing to do, Windows boss Jim Allchin said in the memo. He urged the volunteer beta testers to put the pedal to the metal and send in more feedback.

RC1 is the version that independent software vendors should use to test application compatibility, ahead of the release to manufacturing, he said.

You’ll notice a lot of improvements since Beta 2. We’ve made some UI adjustments, added more device drivers, and enhanced performance, Allchin said. We’re not done yet, however – quality will continue to improve.

The candidate will soon be distributed to a broader base of users, through its TechNet and MSDN sites, Allchin said.

While the release is a mark of progress, and comes after five years since the last full Windows release, there’s still a question mark hanging over Microsoft’s announced release dates for Vista.

Enterprises are supposed to be able to get their hands on the gold version in less than three months, with PC makers and retailers serving the consumer market going to market some time in January.

Amazon.com has started listing Vista’s home versions as available for shipping January 30, 2007, but Microsoft has so far not confirmed that date.

Indeed, Bill Gates said earlier this year that there was only an 80% chance that Microsoft will hits delivery deadlines, already many times delayed. And some Microsoft watchers have publicly called for it to be delayed until all the creases have been ironed out.