Before Windows 8 was officially released a final copy of the software was leaked online, and people were able to use the software bu activating it through a third party KMS server, this would allow users to use the software for 180 days.
After this period, the pirated copy of Windows 8 would need to be reactivated, but now it would appear that Microsoft has inadvertently given pirates the chance to turn their pirated software into a legitimate copy of Windows 8.
Microsoft is giving a free Media Center upgrade to any Windows Pro users until the 31st of January 2013, and now it would appear that this free upgrade will turn the pirated copy of windows into a full activated version.
The guys over at The Verge tested this out by downloading a pirate copy of Windows 8, and then were able to turn it into a fully activated version by the method above, Microsoft have yet to respond to this, as soon as we get some more details we will let you guys know.
Source The Verge