Sorry for the late reply but I wasn't having internet access over the week-end.
I've created the folder hierarchy manually (BTW, you can't create C:\Users when you already have C:\Utilisateurs as Vista recognizes it's the same). That allowed me to start the game.
But as for Kazcroot, the game freezes at the battle screen : it shows the map, you see teh animated water, then the water animation stops and nothing happens. You have then to get the task manager to kill the game.