Back in May, Redmond based OS giant had announced that all those who would purchase a Windows 7 based system between June 12, 2012 and Jan. 31, 2013 can upgrade to Windows 8 Pro for $14.99 or £14.99 or equivalent price depending upon the country they are in. As of now Microsoft has made public the registration through windowsupgradeoffer.com for users in 140 countries.
The Windows Upgrade will ask for your personal details for registration after you select your country. Also you would be required to enter information about your new PC along with date of purchase, the name of the retailer, the PC brand and model. You should also keep your 25-digit Windows 7 product key handy for the upgrade.
According to The Verge Windows 8 standalone copies will be costing $69.99 at launch and after January 31, 2013 the prices will be increased to $199.99.