Kael
Deity
My Steam version did not have the '3.17' key in the registry, I added it manually and it's installing now. No clue how you'd test the actual version number without that key...
You could perhaps assume that, since Steam has an automated updater built-in, everyone with a Steam version will be up-to-date? While it's not guaranteed, I think you'll get less trouble this way than by asking all Steam users to edit their registry manually...
Are you sure it isnt in HKEY Current User?