Microsoft launched a program to help ensure that PC refurbishers and OEMs reselling used PCs to businesses are installing legitimate copies of Windows on them.

The Microsoft Authorized Refurbisher (MAR) program lets OEMs (original equipment manufacturers) that take old computers and rehab them for resale license Windows for those PCs in bulk. The program, launched Friday, is an extension of Community MAR, which was aimed at charities, educational institutions and nonprofits.

Windows licenses are tied to the computer for which they are acquired. PC refurbishers can reinstall Windows on a rehabbed PC if they have the correct proof-of-purchase documentation -- called a Certificate of Authenticity -- and the original OS image software necessary to return the PC to its original state. However, it's often difficult to have both of these items handy for old PCs, and companies reselling used PCs will sell them without an OS installed. This leaves the PCs open for people who buy them to install Linux or a pirated version of Windows.

The new Windows licenses for refurbished PCs that are available through MAR are the Windows XP Home for Refurbished PCs and Windows XP Professional for Refurbished PCs. Microsoft's public relations firm did not respond to questions Friday about how much these licenses cost.

However, Jake Player, president of TechTurn, an Austin, Texas, company that refurbishes PCs, said Microsoft is offering the licenses at a "significant" discount over what they would cost at retail. He said he was not at liberty to disclose how much the licenses cost or what that discount is. TechTurn has been refurbishing and reselling PCs since 1999.

Microsoft also is making a tool available to OEMs and refurbishers through the program that helps them install Windows in bulk on rehabbed PCs.

According to Microsoft, based on research from Gartner Group, refurbished PCs make up about 10 percent of the worldwide PC market. Companies often don't know what to do with PCs they no longer use and some of them languish in closets or are thrown away, creating industrial waste. Microsoft wants to encourage the reuse and resale of these PCs through the new program and ensure a genuine copy of Windows is on them when they are resold, the company said.

Player said that before MAR, his company would sell a refurbished PC without an OS or purchase a copy of Windows at retail and install it on the PC before resale. He said that whether it happens intentionally or unintentionally, some of the PCs that are distributed without an OS do end up running an illegitimate copy of Windows.

MAR marks the first time Microsoft has clarified when reloading the original Windows OS on the PC is legitimate and when it's not, Player said. He said he's pleased Microsoft is now providing licensing and support for PC refurbishers through the program.

Microsoft has been stepping up antipiracy efforts through a program called Windows Genuine Advantage, mounting numerous lawsuits against companies and individuals it claims are distributing pirated or counterfeited versions of Windows. The program also includes automatic checks on Windows PCs to ensure users are running a genuine copy of Windows. These checks will limit the functionality of a PC with a copy of Windows that is found to be pirated.

The MAR program is currently open to existing Microsoft OEM partners worldwide and to other OEM or non-OEM PC refurbishers in North America. Eventually, Microsoft plans to extend the program to refurbishers outside of North America, the company said.