The offer came as Microsoft prepares for the official launch of Windows 8 this week. They also qualify if they buy a new PC that comes with Office 2010 preinstalled during the eligibility period. To get the upgrade, customers will need to provide proof of purchase, dated between 19 October, 2012 and 30 April, 2013, and a valid product key. The other Office for Mac versions will only provide upgrades to one-year Office 365 Home Premium subscriptions. Specifically, Office University 2010 customers, both on the PC and Mac, will get to move for free to Office 365 University, on a four-year subscription. Those on other versions can only upgrade to variants of Office 365. People buying Office 2010 now will get a free upgrade to Office 2013 when it arrives, Microsoft has said.