ZDNet has the news:
"The company will begin testing its hypervisor software, developed under the code name Viridian, by year's end, Bob Muglia, senior vice president of Microsoft's Server and Tools business, told CNET News.com. The software will ship within six months of Longhorn Server, the next major release of the company's server operating system, due in the second half of next year".

Don't miss the announcements at WinHEC in tomorrow's keynotes!