If you want to move a program from your hard drive to an external hard drive your best option is to uninstall the program and then install it on the external hard drive. Make sure to choose custom when prompted for the installation directory and choose you external hard drive folder.

If you try to directly copy all your files from your hard drive to the external hard drive in most cases the program will not function since the registry and other settings will still be pointing to the original hard drive path.