It's true you are only allowed one Sage 100 installation, however, that does not prevent you from having more than on MAS90 folder. I simply install Sage 100 once, then copy the MAS90 to another location and manually change the shortcut to match the new location. If I need to install updates, etc., I simply move the MAS90 folder back to the original location by juggling folder names. I haven't come across any problem, so far.