The National Aeronautics and Space Administration is the latest federal agency to put a hold on PC upgrades to Windows Vista. NASA has decided against deploying Microsoft's five-month-old operating system anytime this year.

The decision puts NASA in company with the Federal Aviation Administration and the U.S. Department of Transportation, both of which in February revealed temporary bans on Vista.

NASA has set January 2008 as a "target" for beginning the transition from Windows XP to Vista, according to a spokesman for the federal agency, which has approximately 60,000 Windows PCs.

NASA typically waits until a service pack is released for any new operating system to ensure stability, the spokesman says. (Microsoft has not indicated when it will release a service pack for Vista.) The interim also will be used to ensure that NASA's applications are compatible with Vista and that its PCs meet the hardware requirements needed to run the operating system.

In a meeting with IT professionals and user-group representatives last week on Microsoft's campus, CEO Steve Ballmer rejected an assertion by a NASA computer scientist that Vista has been banned by most sectors of the federal government.

"Vista has been anything but banned from most parts of the U.S. federal government," Ballmer said, adding that he anticipated near-term adoption in "a number" of government accounts. He stopped short, however, of naming any government agencies that are in the process of deploying Vista or about to do so.