Broke 0.5 Vistas Fixed officially acknowledged Aug 24, 2007 their #44 worst broke on record

The servers that verify you paid decided you hadn't

Windows Genuine Advantage outage flagged licensed Windows as pirated

↳ caused by WGA validation outage (August 2007)

The market's verdict: +0.5% on MSFT in the week after.

Status: Fixed. Working as intended, eventually.

What actually happened

Starting the afternoon of August 24, 2007, Microsoft's Windows Genuine Advantage validation servers failed worldwide for roughly nineteen hours. Properly licensed XP and Vista machines failed validation, so Vista treated their owners as pirates: Aero switched itself off, ReadyBoost went dark, and the desktop picked up a persistent nag that could not be argued with, because the thing you would argue with was down too. Microsoft later blamed human error, pre-production code that reached production servers. The system built to catch non-payers spent a weekend accusing the paying ones. Validation was restored by the 25th, and trust returned on its usual schedule.

This one is officially acknowledged.

Were you affected? Unbreak it

Validation restored within a day

Microsoft has acknowledged this issue; a fix ships in an out-of-band or next cumulative update. Check Windows Release Health before manual workarounds.

They did it more than once

Later, again: The "optional" update that un-licensed the Office you paid for (Sep 2026)

2007: called the paying customers pirates. 2026: switched their Office off.

Timeline

Aug 24, 2007 Confirmed First reports came in.
Aug 25, 2007 Fixed Validation servers restored after ~19 hours.