You don't have to, and shouldn't, touch anything

Spoiler Alert, click show to read: 
If you must mess around with the security settings, and you have one of the 'better' versions, launch secpol.msc from the start menu (I think it's only there in Vista Ultimate, Business, and Enterprise), go to local policies > security options and you can tweak UAC there.

It's not a good idea to do what I did and turn it off