if you have an english windows version, the path may be C:\program files\rebound\datafiles. The space in between program and files could cause problems, so install rebound into a folder without any space within its path.
the other opportunity is to press start->search. then search for a folder called datafiles.
Please go to
http://www.hammerslam.org and use the forum. I have a lot of work with the tool and this would save a lot of time. Thx