I have Microsoft Security Essentials on a Windows 7 system. How do I get rid of Windows Defender?
Also check out this article: How To Remove Windows Defender & Why You Might Want To
This is a good quick how-to for you:
To turn off Windows Defender you can either:
1) Launch the program, click on Options, choose Administrator and uncheck "Use this program".
2) Click Start, and search for "Run", then choose it when it pops up. Type "services.msc" and hit OK. Scroll down till you find Windows Defender, right click and choose Properties. In the dialog that pops up find "Startup Type" and in the drop-down box hit "Disabled".
This won't remove it altogether, but it will be disabled and you will be able to use your favourite spyware buster.
I recommend Malwarebytes and Spybot S&D as two excellent free alternatives.