Microsoft is hoping to beat the fraudsters and trace large-scale counterfeiters of Windows XP OEM with a free checking and replacement scheme for users.
Alex Hilton, licence compliance manager at Microsoft, said the vendor will provide a maximum of five copies per user.
"We don't want to open the floodgates to recycling counterfeit software," he said.
"We're not looking to prosecute or pursue people who have bought the software. We want to trace it back to the source."
Microsoft noticed higher-quality counterfeits of its Windows XP Home and Professional Editions on the market, and started the Windows XP Counterfeit Project in the US last year.
Hilton said he does not know how many people are likely to take up the offer in the UK.
"We want to protect the legitimate channels and protect our customers," he said. "The only way Windows OEM should be sold is installed on a new PC. Frankly, the majority of counterfeit product we see in the market is [fake] XP OEM."
Users who want to have their software tested will have to post in their software, complete a witness statement and enclose other information, such as receipts. They will receive a bona fide copy of Windows XP if their software turns out to be fake.
Software must be sent in before 31 December and excludes upgrades or copies bought under a volume licensing agreement.
Martin Breffit, director and co-founder of system builder a-sure, said: "I can see the rationale behind this, but I do wonder about the uptake.
"What's the benefit to the user apart from getting a bona fide copy? I don't know whether many people are going to admit they have bought a counterfeit copy. I suppose this is another route to finding rogue traders."
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