Software pirates have been exploiting a Microsoft promotion to get a free copy of Windows 8 Pro.
Microsoft has been offering users the chance to download the Windows Media Center (WMC) add-on for Windows 8 without charge until January 2013.
However, users have found that the product key generated to install the add-on can also activate preview editions of Windows 8.
The method was outlined on Reddit, by a user known as noveleven.
"Microsoft is giving away free upgrade keys to turn Windows 8 Pro into Windows 8 Pro+WMC [Windows Media Center, which is a separate add-on for Windows 8], and they don't bother to check if the key you are currently using is valid.
"As long as the system is activated, even if it is activated with KMS [Key Management Service], it will take the key and apply the upgrade.
"Since the WMC key comes directly from Microsoft and is unique for each user, it activates Windows 8 Pro permanently. Oops!"
With previous editions of Windows, pirates used to bypass the need to purchase codes by activating multiple copies using "volume keys".
These 25-digit activation codes were used by PC vendors to economically activate mass numbers of Windows machines. However, they were prone to being leaked out.
Scamsters even used to game Microsoft's phone activation system to install multiple copies of operating systems, such as XP.
Despite Microsoft beefing up activation for Windows 8 (each copy requires a unique code), this flaw appears to have been pounced on by a number of pirates.
Currently, Microsoft is claiming that a product key to activate WMC will be sent within 72 hours.
Microsoft has yet to confirm whether the flaw has been plugged.
