How does UAC protect single user on home computer?

I would like to know if UAC is really necessary for a home user who is the
sole operator of his/her computer. It seems that most of the security is
aimed at preventing actions from non-authorized users, but that doesn't
apply if no one else uses one's computer. Would it be safe to turn off UAC
under those circumstances since you would be protecting from yourself? Or
does it it some way also protect the user from viruses, etc.? I already
have a virus program and use the MS firewall, as well as a router. I'm of
course going to give myself permission to do something I just asked to do
(like delete a file, move a short-cut, install a program, etc.) so UAC just
causes an annoying extra click or two. Please advise if I am wrong.
Thanks!

Hello,

UAC is designed to make sure you are approve of any action that is taken by
a program on your computer that could potentially harm your computer.

This is especially useful in home situations.

UAC suppliments virus and firewall detections. If a virus scanner or
firewall fails or you run a bad program that isn't detected or that doesn't
fall into those categories, UAC is your last line of defense.

UAC will also limit damage that viruses or spyware can do if they do happen
to get installed onto your computer.

Unless you have a very good specific reason to disable UAC, you should leave
it on.

- JB

Vista Support FAQ
http://www.jimmah.com/vista/