Hmm... seems like Microsoft might be making a useful (if long overdue) improvement with regards to account security. Like almost everyone, I use XP with an admin account so that I have a fully functioning PC, and don't have to log in/out/in again just to do a minor app. install.
Even worse, when I setup a new PC for my parents in-law recently, I set up the one and only account as admin, as I knew they would not cope with the complexity of using two accounts, etc.
If Vista simply prompts you for the admin password when it is needed (like unix

) then that is a useful security improvement as it makes it easy enough to use that people will use it.
The parental controls sound good in principle but I suspect many parents won't be bothered/the kids will find out the admin password and take control!