Microsoft Corp. said today that it will make the prized source code for its Windows operating system available to several governments and governmental agencies, as it tries to stem defections to competitors' software.

The company has already signed agreements with the Russian government and NATO to allow them to review free the underlying programming instructions that Microsoft has long guarded, and it is considering agreements with more than 60 other countries and organizations.

The decision will let governments evaluate for themselves the security of Windows, Microsoft said. It also will give them the technical data they need to develop their own secure applications to work atop Windows. The governments will be able to view the code but not to alter or distribute it.

The announcement comes as government agencies in Japan, France, Germany, China and the United States are looking into or adopting competitors' software, including open-source, Linux-based systems. Unlike Microsoft's proprietary software, the underlying code for open-source software can be downloaded free, improved and redistributed.

"It's a brilliant maneuver," said Michael Gartenberg, research director for Jupiter Research. "It gives them a huge [public relations] win, gives them a response back to the open-source folks, and also provides the impetus that many of the government organizations have been looking for to continue doing business with them."

Microsoft's "government security program" is similar to its "shared source" program, introduced in 2001, in which it makes some source code available on a limited basis to clients and technology partners.

The Redmond, Wash.-based company is confident governments will respect its intellectual property and isn't worried about piracy or other infringements, said Salah Dandan, the program's worldwide manager.

"The basic business decision that we decided to make here is that Microsoft is willing to trust governments and willing to partner closely with them," Dandan said.