REDMOND, WASH. - Microsoft last week acquired technology that it says not only will help Windows NT 4 users with migrations and server consolidations, but also is a step toward the company's goal of infiltrating corporate data centers.

Microsoft acquired three virtual-machine products, including the corresponding engineering teams and support organizations, from privately held Connectix. Terms of the deal were not disclosed.

A virtual machine lets multiple operating systems run on a single server or desktop.

The three products include software under development called Virtual Server, a native Windows-based server application that lets Windows operating systems, Linux, Unix and OS/2 run concurrently in virtual machines. Microsoft plans to ship a beta version by midyear and a general release by year-end.

The other two products are Virtual PC for Windows, which lets various versions of Windows, and NetWare, IBM OS/2 and Linux, run on the same desktop; and Virtual PC for Mac, which lets Windows applications run on the Macintosh.

Microsoft says Virtual Server will let the company's NT 4 installed base take individual NT applications running on separate servers and consolidate them onto a single box running alongside Windows 2000 or Windows Server 2003.

IDC predicts that 75% of large corporations will consolidate portions of their servers this year, with the Win 2000/NT market spending more than $1.3 billion to do so.

"Users have said they don't want abrupt change where they are forced to migrate all at once, and they don't want to have multiple servers in use during migrations," says Dan Kusnetzky, program director for operating environments and serverware at IDC.

But he says the Connectix products might force Microsoft to do two things it doesn't want to do: support a product that runs Linux, and change its licensing model.

"Microsoft licensing is device-focused," he says. "In the virtual world, that licensing is not very equitable."

But those might be short-term issues, experts say, because Microsoft wants to move Windows into the corporate data center and compete with Unix and mainframe system suppliers. To do that, it needs virtual machine, partitioning and workload management tools.

The company has a first-generation workload management tool slated to ship with Windows Server 2003 called Windows System Resource Manager.