A: To access the Windows Store, the user must have a Windows Live ID, which is used to track and purchase Windows Store applications. 

Each Windows Store application installation is tracked and can be viewed within the Windows Store application by opening the Windows Store application options (right-click or swipe down from the top of the application) and selecting the "Your Apps" option (see screen shot below). 

All the applications you have ever installed are shown or just those installed on specific machines.

Windows Store Your Apps Display