UAC (User Account Control) is the most obnoxious, nagging  windows that will drive you crazy and frustrate you while using Windows 7 or Vista.

One way to stop being annoyed is to disable it.  However doing so will make your computer less secure.  I in no way recommend anyone disable UAC, but I will provide a quick way to disable and enable via the command line.

Disable UAC

C:WindowsSystem32cmd.exe /k %windir%System32reg.exe ADD HKLMSOFTWAREMicrosoftWindowsCurrentVersionPoliciesSystem /v EnableLUA /t REG_DWORD /d 0 /f

Enable UAC

C:WindowsSystem32cmd.exe /k %windir%System32reg.exe ADD HKLMSOFTWAREMicrosoftWindowsCurrentVersionPoliciesSystem /v EnableLUA /t REG_DWORD /d 1 /f

Both require a reboot to take effect.