Turn Windows Defender on or off on windows vista

http://windows.microsoft.com/en-NZ/windows-vista/Turn-Windows-Defender-on-or-off
1.Open Windows Defender by clicking the Start button , clicking All Programs, and then clicking Windows Defender.

2.Click Tools, and then click Options.

3.Under Administrator options, select or clear the Use Windows Defender check box, and then click Save. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.