A reader recently asked us if she needed Windows Defender, antispyware software from Microsoft that comes with Windows Vista and Windows 7, if she had downloaded Microsoft Security Essentials (free antivirus and antispyware software).
If you use Microsoft Security Essentials, you don't need Windows Defender. When you download Microsoft Security Essentials, it will turn off (but not uninstall) Windows Defender automatically. It does this so that you don't have two programs on your computer that are doing the same thing. If you ever decided to uninstall Microsoft Security Essentials, Windows Defender will be turned back on again.
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That was a clear answer to my question!
very helpful indeed, it has put my mind at rest as a few people have told me that i should have more security
My Windows Defender kept crashing...so I uninstalled it (from my Windows 7 system). I tried to reinstall it, but microsoft insisted that it was still on my system (even though my system itself told me it was gone). So now, if I ever try to do without Microsoft Security Essentials, I cannot turn Windows Defender back on. -- even though the Windows 7 shows that it is still there -- until I try to turn it on. When I do try, of course, it says "Windows Defender does not exist as an installed service." I tried Microsoft support to get help gettin it back, but tech support could not help me get it back.