Hi all..
I know this post is a little late, but perhaps it will help someone else that is looking for help regarding this issue. I also had trouble with the MegaStat program. For some reason, the file you are looking for is called "unwise". The path is:
c/program files/microsoft office/office/library/unwise.exe
Once installed, the MegaStat integrates with your Excel. Go to tools, click on Add-ins, and then click MegaStat. That should do it for you. Whenever you bring up Excel from that time on the MegaStat option link will be to the right top of the screen. If you still have problems and it says you need authorization, bring up Excel, go to tools, scroll down to Macro, and over to security..then set the security to medium. That will give the authorization.
I hope this helps someone.
Spencer St John