Microsoft launched the Microsoft Authorized Refurbisher programme to help ensure that PC refurbishers and original equipment manufacturers (OEMs) reselling used PCs to businesses in the US are installing legitimate copies of Windows on them.

The Microsoft Authorized Refurbisher (MAR) programme lets OEMs that take old computers and repurpose them for resale to license Windows for those PCs in bulk. The programme is an extension of Community MAR, which was aimed at charities, educational institutions and non-profit groups.

Windows licences 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 licences 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 on Friday about how much these licences cost.

Microsoft is also making a tool available to OEMs and refurbishers through the programme 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 programme and ensure a genuine copy of Windows is on them when they are resold, the company said.

Microsoft has been stepping up antipiracy efforts through a programme called Windows Genuine Advantage, mounting numerous lawsuits against companies and individuals it claims are distributing pirated or counterfeited versions of Windows. The programme 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 programme 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.