Uninstall Windows Defender

from that computer and replace it with the free version of
Malwarebytes Anti-Malware 1.41 SUPERAntiSpyware 4.29.0.1004
Click the green icon at each site to download them.
Close all open windows, then install them.
Allow them to update their definition files during the install process.
(Run a quick scan with them about once a week, then allow them to fix EVERYTHING they find. Make sure to update them before running a scan. They're very user-friendly, they do a very good job, and they're well known and recommended in these forums.)
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I'm glad to see that you're not using McAfee, Symantec Norton, or Windows OneCare Live.
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