If the install software won't run, you probably have Stuffit Deluxe
or Standard 8.0.0.

The problem is not with the with the Roni Music software but a
problem with your version of Stuffit Expander.

Either download the Stuffit X version of this file here:
http://www.ronimusic.com/download.htm

or go here:
http://www.ronimusic.com/stuffitbug.htm
and read how to update your version of Stuffit.