At an interoperability conference in Brussels, the software giant said that its Virtual Hard Disk (VHD) Image Format specification can be used by third parties without the need for them to get a commercial license.

The virtualization technology will be available under the terms of Microsoft's Open Specification Promise (OSP), which it introduced in September.

The promise, similar to other pledges not to sue over patents, allows developers to create software based on the Virtual Hard Disk format without fear of infringing on Microsoft patents, company executives said.

"This is Microsoft's personal promise to any individuals or organizations in the world that they can use patented technologies that could be in this VHD technology," said Jean Paoli, the manager of interoperability and XML architecture at the software maker.

Until now, Microsoft has licensed the technology to other software companies for free. The new system cuts out the need for outsiders to sign a commercial license with Microsoft, executives said.