Windows users in China may face serious problems with Microsoft's launch of an anti-piracy tool that turns the user's desktop black if the installed software is not legal.

The Windows Genuine Advantage program turns the user's desktop black if the installed software fails a validation test. This is Microsoft's latest weapon in its war on piracy in China, where the vast majority of 200 million computer users are believed to be using fake software.

The company announced a week earlier that the anti-piracy software would be automatically installed on users' computers through a typical Internet-based updated mechanism. If a computer fails a validation test, the desktop changes to a plain black background when the computer is restarted.

Chinese Internet users have expressed fury at Microsoft's launch the anti-piracy tool.

Dong Zhengwei, 35, a Beijing lawyer, described Microsoft as the "biggest hacker in China with its intrusion into users' computer systems without their agreement or any judicial authority," as he was quoted by the China Daily newspaper.

"Microsoft's measure will cause serious functional damage to users' computers and, according to China's Criminal Law, the company can stand accused of breaching and hacking into computer systems," he was quoted as saying.

Dong also filed a complaint with the Chinese Ministry of Public Security on Sunday, accrding to the paper.

Although a few instances of screen blackout were reported on the first day of the action, Internet experts and industry insiders have expressed grave concern at the move.

The China Software Industry Association (CSIA), the only software industrial organization in the country, is also planning to take action against Microsoft.

Microsoft defends the program on its website as "part of Microsoft's commitment to help protect its intellectual property and to help you avoid problems before they happen."

Microsoft on Thusday announced Global Anti-Piracy Day, a simultaneous launch of education initiatives and enforcement actions in 49 countries on six continents to combat the illegal trade of pirated and counterfeit software. The programs include intellectual property awareness campaigns, engagements with partner businesses, educational forums, local law enforcement training, and new legal actions against alleged software counterfeiters and pirates.