Thanks for your replies. Sorry I didn't get back to them earlier, my spam filter ate them.
Vaughan, you're correct, I was meaning OS-level privileges.
The single/multi user issue is a sticky one. Basically, I think the program doesn't really suit a database model, which is why we're writing a new version. It's most similar to a normal program, any user should be able to use it and they each have their own preferences etc., but since there can only be one back-end for the runtime everyone would be sharing the same prefs. Therefore, we decided to go with one copy per user.
Anyway, unless there is a better location for it than the AppData directory we'll just go with that.
Thanks for the help,
Graham