3) Click on "Sauvegarder les clés de la base de registre d'une installation de RBR"
4) Click on "Supprimer les clés d'une installation de RBR dans la base de registre "
5) Install the game again.
6) Do the same for your second installation.
7) Run the add-on you want to install (Cz or RsRBRlive08)
You can find two registry keys in your Rbr folder's:
"Sauvegarde des cles RBR Installation 1.reg" for installing the rbr version
"SupprimCleUninstallRBR.reg" for deleting (virtually !!!) the rbr version
Then you have just to click on the good registry key !