Windows 8 is coming out in the not to distant future, so Microsoft is preparing for this by ensuring no slump in sales before Windows 8 hits the shelves.
Microsoft will be offering 138 countries a promotional upgrade to Windows 8 Pro edition, as long as they buy a qualifying Windows 7 Computer between June 2nd 2012 and January 2013. The upgrade in 2010 caused a bit of a uproar, as it was supposed to be free, but then a £20 shipping fee was added. This time, they are doing the same thing, but making it clear there is a small fee.
So make sure you keep your receipts and purchase from tomorrow with confidence. More info about the promotion will be available closer to the release date.