Windows Defender or Windows itself has a profoundly dumb feature that turns Defender OFF if it detects another anti-spyware or anti-malware program. For example: an XP machine running AVG anti-virus (free or paid version) and Defender - Defender will turn itself off (or Windows will turn it off) when the Anti-virus program is detected. The same behaviour is demonstrated under Windows 7 - Defender will not stay running - and stops without user warning. I need to find a method in the registry that will preclude this aberrant behaviour.

Hi, To answer your question, Windows Defender will be disabled automatically after installing certain antivirus program, such as Windows Live OneCare, Forefront or Security Essentials. Also, some third party antivirus program will disable Windows Defender after installing the software since the software already includes most of function about Windows Defender. To protect the system and improve the performance, you can keep turning off Windows Defender. Thanks, Novak