Microsoft is updating its Windows Genuine Advantage (WGA) software to make life more unpleasant for those using pirated code.

The changes to the software include replacing the wallpaper on the desktop with a black screen every 60 minutes and permanently displaying a message warning that the user is running a pirated operating system.

“I'm excited about how this release balances our goals of providing a great experience to those who have genuine Windows, and at the same time, creating a compelling experience for those who have non-genuine copies to get genuine Windows,” said Alex Kochis, director of the Genuine Windows programme at Microsoft.

“As usual, I welcome your feedback about this latest release and the programme overall.”

The changes are being rolled out on the most commonly pirated Windows operating system, Windows XP Pro. The same system may also be included for other operating systems.