The company said that Release Candidate 2 of theis being made available to its usual crop of technical testers and developers, as well as to some of the enthusiast consumers who are testing the earlier, RC1 version.
Microsoft did not change its timing for the software's final release, but did indicate that it could still miss its goals.
"As we stated from the beginnning of Windows Vista development, the quality of the product will always be our first priority," Microsoft said in a statement. "That said, Microsoft continues to target Windows Vista availability for volume license customers in November 2006 and general availability in January 2007, although the final delivery will be based on quality."
The software maker had hoped to have Vista on store shelves and in new PCs in time for this year's holiday season, but said in March that it would.
Analysts have been divided on whether Microsoft will make its revised goal. Goldman Sachs analyst Rick Sherlund said earlier Friday that Microsoft was, but Gartner has been predicting for some time that Microsoft would be forced to again delay the product.
The software maker is encouraging developers and others to provide feedback on any issues that remain unresolved in the latest test builds.
"Microsoft has continued to receive excellent feedback that is helping to improve the overall quality and performance of the product," it said. "RC2 reflects that feedback and includes important improvements in performance, application compatibility and 'fit and finish' work."