http://windows.microsoft.com/en-us/windows-10/about?ocid=WIN10_0_WOL_Hero_Home_Windows-10_Null_01
Great news! We will offer a free upgrade to Windows 10 for qualified new or existing Windows 7, Windows 8.1 and Windows Phone 8.1 devices that upgrade in the first year!* , And even better: once a qualified Windows device is upgraded to Windows 10, we will continue to keep it up to date for the supported lifetime of the device, keeping it more secure, and introducing new features and functionality over time – for no additional charge. Sign up with your email today, and we will send you more information about Windows 10 and the upgrade offer in the coming months.
網站寫的很清楚，只要在一年內免費升級，就可以持續一直使用到電腦掛掉..
