Very few programs actually ask me to approve them everytime I run them, in
fact, hardly any. If your argument is correct, then all those programs
could
be run be a "rogue" program. So what exactly is being protected?

If a program does NOT ask you to approve it when it starts, that program
DOES NOT have administrator power, even if you are logged in as an
administrator. Only programs that ask you for permission when they start
have administrator power.

This means that unless you give an application permission when it starts, it
is impossible for it to do such things as delete/modify/create any file that
you do not have specific write access to (such as system files, program
files, etc), change/create/delete registry settings that affect the entire
computer, load drivers, change system settings, etc.

In essance, programs run as a "limited user" as defined by XP unless they
prompt you for permission, or you right-click them and click Run As
Administrator, in which case they run as an administrator.

I thought
that was what anti-virus and programs like Defender were for?

The anti-virus and defender programs detect known malware and remove them
for you.

UAC is designed to allow you to choose which programs have complete access
to your system. This allows you to prevent programs that you do not trust
from gaining access to your computer. Using UAC, you can help prevent
unidentified malware from getting onto your system by being vigilant;
however, that is not the explicit purpose of UAC - UAC is meant to give you
the supreme control over which programs have complete access to your
computer, for you to use as you see fit.

Do you
actually have to give permission every time you run every program? I have
UAC turned on, and it is only one or two that require it every time.

No, only those programs that ask for administrator power will need to be
approved every time they are ran.

--
- JB

Windows Vista Support Faq
http://www.jimmah.com/vista/