Microsoft has released updates for Windows 7 and 8.1 which provide support for additional Windows 10 upgrade scenarios. Here are the details.
Some users trying to upgrade from an the older Windows operating systems to Windows 10 may have encountered issues during the process. Microsoft is attempting to fix some of these problems with the most recent updates to "provide a smoother experience when you have to retry an operating system upgrade because of certain failure conditions".
The updates also allow Microsoft to better "monitor the quality of the upgrade experience".
For Windows 8.1 and Windows Server 2012 R2 users, the update is called KB3112336. As for Windows 7 and Windows Server 2008 users the update is KB3112343. Both updates are optional through the Windows Update tool.
[Via Microsoft Support]