[Mittelwaechter]

Ubisoft didn't want to pay the upgrade cost for any StarForce updates available with Vista supporting the "old" SH3 software.
If you run Vista or any later operating system the original StarForce drivers won't be compatible, while any up to date StarForce drivers won't be compatible with the game.

Catch22.

The good news: the drivers won't install as long as you don't start the game.

To get you aboard you'll have to install the game NOT into the default path but something like C:\games\... - or whatever UAC unprotected path you think fit.
Don't start the game, don't install any 3rd party software provided with your DVD.

Check the installation directory for the Sh3.exe and rightclick it.
Select Properties and the tab Details to read the version number of your Sh3.exe.

If it is 1.0.0.0 you have the original, unpatched, starforced version.
Starting the game will install the incompatible StarForce drivers and you've messed it up.
If it reads 1.4.0.1 you have a patched and (pretty sure) starforce free installation.
To check it, remove the DVD and try to start the game. If it works you are good to go - otherwise install the five files.

With 1.0.0.0 you'll have to patch to 1.4b and install the five files to get rid of the game checking for StarForce and the DVD.
It doesn't have any consequences with other starforced software, as long as you didn't install the old drivers and have to remove the StarForce crap with the SF tool.
Only this will interfere with any other StarForce protected game installations.

Report if you started the game and got in trouble - I'll help you getting sorted.
You may have to reinstall the other game, but you will have both - your SF protected game and SH3 modified to unprotected.