Microsoft said today that it is planning to clamp down on software pirates by battening down the hatches on its official download services so that only users of genuine software will be eligible for future fixes and updates.

The crackdown will be administered by extending the Redmond giant's existing Windows Genuine Advantage programme.

Introduced as an optional pilot programme to users of English language versions of Windows in September 2004, the scheme checks the authenticity of a user's software and provides access to free software if the product is found to be genuine.

Microsoft claimed that more than five million people are voluntarily taking part in the programme.

The scheme will expand on 7 February as 20 additional language versions of Windows XP will be added to the programme on the Microsoft Download Center.

From the second half of 2005, visitors to the Download Center and Windows Update will be "required to participate" in Windows Genuine Advantage to download content and software updates.

However, to help customers who "may require more time to move to genuine Windows software", Microsoft said it will offer security updates through the Automatic Updates feature in Windows, with or without Windows Genuine Advantage validation.

After the February deadline Download Center users with Norwegian, Czech and Simplified Chinese language versions of Windows will be required to participate in the programme.

The carrot and stick approach will see Microsoft offer incentives in the form of a software giveaway valued at more than $450 for each user of genuine Windows software who takes part in the programme. The free software will include:

In addition Microsoft will begin piloting a "legalisation offer" in China, Norway and the Czech Republic for "qualified participants who discover that they have been sold a counterfeit version of Windows XP". These customers will be offered a genuine version of Windows at a reduced price.

"Software piracy costs customers, software vendors and national economies billions of dollars every year. The best way to fight software piracy is to ensure that users recognise and receive all the benefits of genuine software," said Will Poole, senior vice president of the Windows Client Business at Microsoft.

"When our customers participate in Windows Genuine Advantage, they will know they have easy access to updates, added-value software offerings and other benefits of genuine Windows XP, not the uncertainty and risks of counterfeit software."

According to a survey by the Business Software Alliance, over a third of the software installed on computers in 2003 worldwide was pirated. And a survey by Microsoft suggested that UK users are hypocritical about software piracy.