Microsoft has kicked off the Windows 8 Upgrade Offer program for customers who purchased a Windows 7 PC between June 2, 2012 and January 31, 2013. Until February 28, 2013, these users will be able to upgrade to Windows 8 Pro for just $14.99 (14.99EUR).
You can find the details at Windows Upgrade Offer, the promo code will be send via e-mail after Windows 8 is generally available on October 26, 2012.
Microsoft is trying to boost popularity of its upcoming operating system by making it available cheaper than ever. Existing users of Windows will be able to upgrade to Windows 8 Pro via digital distribution for $39.99 and via a physical DVD for $69.99, but both offers expire on January 31, 2013.
The non-promotion price of Windows 8 is still unknown, but according to The Verge prices may jump from $69.99 to $199 once the upgrade offer expires.