Microsoft Corporation on Tuesday rolled out its Vista, the much-delayed Windows operating system, for the last and most critical round of testing and announced the final product will be in markets as scheduled.

Microsoft’s chairman Bill Gates released the final test version of Vista, called Beta 2, along with test versions of its Office business software suite and Longhorn server software, at the company’s annual conference for hardware developers. He said the release constituted “a significant milestone.”

The company had originally scheduled the release of Vista in late 2005, but delayed it until mid-2006. Jim Allchin, the company’s co-president of platforms and services division, said the software would be ready for consumers by January and for corporate customers this November. More