Ahh now this little hurdle.
Install it under admin. Then run it under desired user, take a note of all error messages. In the message there should be a reference to a file. Remember it. Login as admin again, go to that file and change its permission to let that particular user have full control too (read write change blah blah blah). Continue doing this until there are no error messages. Hey presto it works!
Note I did this at the beginning of this year so I may have misremembered it. Now thinking about it I even could have installed under a non-admin user, but I'm sure I had to do the permission thingo. The files you have to change are under the Winnt folder if I remember rightly.
Get back to me if you have problems, I will try to remember better .
Oda