MICROSOFT WINDOWS 10
Microsoft is planning to release a Windows 10 technology public preview sometime between the end of September and the beginning of October.
Great news! Microsoft 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 (exceptions apply).
Microsoft is expected to release Windows 10 "later in the year" in 2015
Read more here.