Disabling UAC in Vista
If you're using Windows Vista and have found the new User Account Control elevation prompts annoying, you can easily disable the prompts by adjusting the Group Policy settings under Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options\User Account Control: ...
However, you can also apparently completely turn off UAC if you just find the notion of not running as administrator unless you need to, annoying. If you open the User Accounts Control Panel, you'll see an option that says "Turn User Account Control on or off". If you click that link, you can completely enable or disable UAC. Note however, that changing this setting requires a reboot. Also, one other thing I noticed is that changing this setting seems to wipe all browser state (e.g. cookies and passwords) when I logged back in. This is probably because the IE Protected Mode state that is enabled when UAC is enabled writes this kind of data to virtualized file system and registry locations, which obviously go away when UAC is disabled. That's my guess anyway.