No luck, but I haven't much experience with Vista yet. If I understand you right, you can install the update, but as soon as you turn your back your PC installs the old version again.

This sounds strange, but could be related to your access rights to the Gamestudio folder on your machine. Normally you can indeed not modify the folder, but you can when you run the update with the option "as administrator" as suggested here. So at the moment I don't see the reason for your problem. I'll try to learn more about Vista and will notify you when I find out something.