What is the Reserve Upgrade app?

Microsoft  released Windows 10 as next generation operating system PC's, Tablets and Mobile devices t.Windows 10 was free for the first year to all Windows 7, Windows 8.1 and Phone 8.1 users. The Reserve Upgrade app means how

Windows 10 would be distributed and how you can reserve your copy .

Windows 10 was free for the first year to all Windows 7, Windows 8.1 and Phone 8.1 users.

That's cool, but what does that mean? that means you  will have to pay for Windows 10 after the first year! No. Its just a promotion to get as many users to upgrade their existing Windows 7 PCs and Windows 8.1 devices to Windows 10. Once you upgrade, its yours forever at no additional cost. As Microsoft Program Manager for Windows Terry Myerson described it:

This is more than a one-time upgrade: once a Windows device is upgraded to Windows 10, we will continue to keep it current for the supported lifetime of the device –at no additional charge.

Source: http://blogs.windows.com/bloggingwindows/2015/01/21/the-next-generation-of-windows-windows-10/