The software maker said that the Release Candidate 1 version offered up earlier this month is now being opened up to consumers who were not already testing the new operating system.
Microsoft is looking for more testers, as it works to iron out the bugs in Vista. After several delays, the company hopes to release Vista to large business customers in November and start selling it broadly in January.
"RC1 represents a significant industry milestone on the road to delivering Windows Vista, and customer participation and feedback are integral parts of the development process," Microsoft said in a statement. "The feedback received thus far from testers has been extremely valuable, and Microsoft expects that by expanding the (customer preview program) with RC1, the Windows Vista team will gather even more worthwhile input."
In all, Microsoft expects to make the latest test version available to about 5 million people.