To prevent the security pop-up in the System Tray, right-click the red
shield (or Control Panel > Classic View > Security Center) and click 'Change
the way Security Center......' then choose 'Don't notify me and
don't........'.
You don’t have to turn UAC off, you can stop the prompt without UAC losing
its security strengths, in Vista Home Basic and Vista Home Premium click the
Windows Orb (Start), type regedit, press Enter and navigate to registry key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
and change the value of ConsentPromptBehaviorAdmin to 0 (zero) from 2.