When trying to install Quickmap Data, you may get this error:

Quickmap Data Installation Failed

The process cannot access the file
‘C:\Quickmap\Data\legal\App\APP_NTH.QIK’ because it is
being used by another process.

This may be because there is another instance of Quickmap that is running and accessing the data, or an antivirus program may be using the file so it cannot be accessed by the Quickmap Data Installer. Another possible cause of this problem is that the user running the Quickmap Data installation program doesn’t have permission to update the files in the data directory.

Addendum: This issue can sometimes be fixed by reinstalling the data after a reboot.