Currently Family Reunion Organizer writes temporary files in its program folder (which Vista and Windows 7 don't like).  If you install Family Reunion Organizer off the C: drive instead of in the Program Files folder, it will run under Vista or Windows 7.

If you have any concerns, download the free trial version at:

http://rootsmagic.com/Try/Family-Reunion-Organizer/

and install it to try it first.