Microsoft has taken desperate measures against fake software. The company is set to challenge software pirates' increasing skill at creating counterfeit versions of Windows XP by launching a programme to verify whether consumers' software is legitimate and replace fake versions with authentic goods.

The pilot programme is aimed at tracking down counterfeit versions of Windows XP that come pre-installed on new PCs sold by systems integrators. Microsoft is hoping to glean information on counterfeiters and their techniques for creating what company representatives have characterised as "high-quality" fakes of Windows XP.

Not only has the piracy rate increased in recent years but the "level of sophistication is unprecedented," said Alex Hilton, licence compliance manager at Microsoft UK.

Consumers who suspect that their software may not be legitimate can send it in for analysis. If Microsoft finds the software is counterfeit, it is offering to replace it for free, with certain terms and conditions, such as a proof of purchase.

Microsoft is hoping to make customers aware of the difficulties they face in not having legitimate software. Companies that buy PCs with pirated software not only face legal concerns, but could find that their network security is compromised, he said.

This programme is part of a broad effort by Microsoft to stem worldwide piracy, which is estimated to cost the software maker billions of dollars a year in lost licensing revenue, it said.

The programme is currently limited to UK residents who purchased Windows XP preinstalled on a new computer before 1 November. Submissions must be received by 31 December.

While other markets have much higher piracy rates than the UK - which has an estimated rate of about 29 percent - it might be too financially prohibitive to offer the exchange programme in those countries, Hilton added.