Yes you are right Kanopus,
but by copy *.dll and *.exe files as described, you have a portable installation.
The directory ("E:\Garmin maps\Maps") can be on removable media (USB flash or even DVD) and be used/moved to any PC.
At least MapSource will run - maybe you need to install BaseCamp to get .NET and C++ objects if you want to use BaseCamp/HomePort.
If you only need MapSource you can download the USB drivers from Garmin(garmin.com -> Support -> Software -> Additional Software -> USB Drivers)
/Merka