After declaring the 21 October as "Global Anti-Piracy Day", moves Microsoft has made with anti-piracy tools have angered many users in China.
People have "flooded" blogs and online forums arguing the company has violated their right to privacy, with some accusing Microsoft of hacking.
The new tool in the Windows Genuine Advantage anti-piracy programme turns users on-screen background black every hour if the installed software fails a validation test whereas previous versions simply notified users their product was counterfeit.
Microsoft said that software piracy was costing billions of dollars. In China, levels of pirated software is said to be as high as 90%.