News 

The Windows Genuine Advantage (WGA) software is intended to validate genuine copies of Windows with the aim of stemming the flow of pirated versions.

But for around 20 hours between Friday and Saturday, users who tried to verify and update their systems found the legitimacy of their copy cast in

ADVERTISEMENT

doubt following server problems which have now been resolved.

For customers running Windows Vista, failing the check limits the functionality of the operating system, disabling the Aero interface, Ready Boost cache utility, Windows Update and some non-critical security procedures in Windows Defender.

"Our data shows that fewer than 12,000 systems were affected worldwide and that many of those have already revalidated and are fixed," a report posted on the WGA blog states.

"This is encouraging news but we want to emphasise that one bad customer experience is one too many and that we're committed to learning from this experience and working to prevent this type of event from occurring again."

Microsoft is encouraging anyone affected by the glitch to revalidate their software at its validation website.