Floater,
For starters, you would need a method of reading the install path from the registry. Then have a user's multiple installs link to that original install path in the registry, switchable by the program that allows multple installs.
Sort of a shell game, where what the current version that the user want is linked to the registry's game path.
The GUI would allow the user to point the utily to each of the SH3 install paths, and link it to the original install path.
For example: 4 installs, original under program files folder, and 3 others under games folder
Install Path #1 (In Registry) = c:\program files\Ubi\Sh3
Install path #2 = c:\games\sh3-v104b
Install path #3 = c:\games\sh3-v104b-oRGyv1.43
Install path #4 = c:\games\sh3-v103
Email me and Im sure I can help you figure it out and test it.
fsimav8r@hotmail.com