hello Jcanning, when the installer for firefox (and many other programs) is executed without administrator privileges it might put its program files into that users appdata directory instead of being installed globally for all users of that machine.

How can we block this please?

hi, since that isn't really a firefox specific question, you could refer to some external resources like https://technet.microsoft.com/en-us/magazine/2008.06.srp.aspx instead.