From yesterday, Microsoft is to require customers to validate that they are running legitimate copies of Windows before they can use its download services.
The Windows Genuine Advantage 1.0 program ensures that customers using Windows Update, Microsoft Update for Windows, and the Microsoft Download Center run a program that checks that their operating system is genuine before they can download updates or content from those services, said a Microsoft spokesperson.
The company has been testing the program since September and has validated more than 48m systems so far, he said. Until Tuesday the program had been voluntary.
Customers who discover they have a counterfeit copy of Windows through the program either will be given a free version of the OS or can purchase it for a discounted price, the spokesman said.
To get a free version of Windows, a customer must fill out a counterfeit report identifying the source of the software, provide a proof of purchase and send in a counterfeit CD of the software. If customers don't have all of that information, they can still fill out a counterfeit report and receive a copy of Windows XP Home Edition for $99 (£57) or a copy of Windows XP Professional Edition for $149 (£86).
Windows XP Home normally sells for $199 (£114) and Windows XP Professional Edition $299 (£172).
The move to lock out pirated copies of Windows from the download sites is part of Microsoft's effort to fight software piracy, which is a major issue for the software vendor.
The company estimates that more than a third of all copies of its software are counterfeit, based on a recent joint report released by the Business Software Alliance and research firm IDC. The study found that 35 percent of software worldwide is pirated. In the US alone, the piracy rate for software is 22 percent.
One issue the software maker faces in fighting piracy is that many users don't know that their copy of Windows is illegal. Windows Genuine Advantage allows customers to solve this problem in a few minutes through the automatic validation.
The Windows Genuine Advantage checking mechanism is anonymous, and includes an ActiveX control on the client side and the Windows Product Activation service on the Microsoft side.
This is not the first time that Microsoft is checking whether installed copies of Windows are legitimate. Windows Update already checks for certain volume license keys that are known to be used illegally to activate copies of Windows.
While counterfeit copies of Windows will be prevented from downloading updates, Lazar says Microsoft is not including security updates in the lock-out. Even customers who do not check their copies of Windows for authenticity will be allowed to download security updates through Windows Update, Microsoft Update for Windows and the Download Center, he says.