I have vista and by windows defender won't turn on

Download and install Microsoft Security Essentials which includes a more robust anti-spyware program than Windows Defender. Carey Frisch

Download and install Microsoft Security Essentials which includes a more robust anti-spyware program than Windows Defender. Carey Frisch

Hi, Please temporarily disable the third party security programs and boot in Clean Boot to check if it is able to turn on the Windows Defender. Please check if the steps in the following similar thread help: Windows Defender Start Error/Can't Find In Add/Remove ProgramsSabrina TechNet Community Support