You can turn off UAC by going to Control Panel > User Accounts and click 'Turn User Account Control on/off'.
To prevent the security pop-up in the System Tray, right-click the red shield (or Control Panel > Security Center) and click 'Change the way Security Center......' then choose 'Don't notify me and don't........'.
However, 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 go to 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.
It’s prudent to create a system restore point before making any changes just in case something goes wrong.