TweakUAC(TM) is a free software tool that you can use to quickly turn UAC (User Account Control of Windows Vista) on or off, or to make UAC operate in the quiet mode:
Using TweakUAC is extremely easy: just download and run it, then select the desired option on its window and press OK.
Turn UAC off: This option turns UAC off completely. If this is what you want, select this option, press OK, restart the computer, and you won't see the elevation prompts anymore. Windows Vista will operate pretty much like Windows XP does when you login to its administrator's account.
Switch UAC to the quiet mode: This option does not turn off UAC; instead, it only makes UAC to operate in the quiet mode. In the quiet mode, UAC does not display the elevation prompts for the administrators. That is, when you attempt to do an administrative task, you will be allowed to proceed automatically, without prompting you to confirm the operation. All other features of UAC would still be enabled: the programs will run with the standard user permissions by default, and the standard users will still see the elevation prompts (the quiet mode applies to the administrator accounts only).
Leave UAC on :
If you have previously turned UAC off or switched it to operate in the quiet mode, you can use this option to restore the original behavior of UAC.
Note that if you turn UAC off or switch it to operate in the "quiet" mode, Vista starts displaying a warning message in its taskbar. You can turn that message off, though: double-click on the shield icon in the taskbar to open Windows Security Center. Then click on the "Change the way Security Center alerts me" link, in the left panel. Finally, choose one of the "Don't notify me" options.
Note also that if you have used the Local Security Policy tool of Windows Vista to change the advanced configuration options of UAC, they will not be affected by TweakUAC; you would have to use the Local Security Policy tool to modify them.