"Just finished cleaning up my infected computer" and "Windows Defender", in the same phrase...
Why I'm not surprised?
Seriously, replace that (IMO) crap of software with one of the many free alternatives out there, like Avira / Avast / 360 TS.
As ondemand scanners use MBAMfree and HitmanPro or HerdProtect.
And add our much-loved Sandboxie!