Q. How many devices can I use with a Microsoft account with Windows 10 Store?
A. For Windows 10 the number of devices that are supported for a single Microsoft account is now 10 for applications purchased from the Windows Store. This is a reduction from the 81 supported with Windows 8.1 but still more than the original 5. The reduction comes from many requests from application developers who wanted to be paid more fairly as it became common for people to buy an application then share their Microsoft account with many friends so they could all use the application without paying. The 10 device limit was deemed a more reasonable number for a single person/family to need.