Great tool. I exclude it and also use it. Not to carelessly turn off Windows Defender (I run mine ON) but because it becomes instances when WD interferes with deep dive program tools I need such as if you delete a very large Gb folder/file and simply delete it still hangs up in $Recycler on disk even after Empty, and causes a defragmenter to stumble & stall because it remains on disk. Then I use a Power User program like PC Hunter or another to Force Delete effectively pulling it off disk where it can no longer interfere with being considered a file. Sometimes if not always, Windows keeps attached software protection on the deleted files in that .old Folder especially after REFRESH. In such situation you insert a UFD and reboot to the parallel screen and it removes easily. (inactive disk) For example on Windows 8 doing a REFRESH Windows leaves Windows.old folder of still protected Program Files/Windows Folder etc. You MUST clear that folder off disk entirely or the silly machine code of windows gets confused (still applies protection token to the system files in it) and I seen programs junction to files/processes in it. Mind you please, this only applies to Windows 8 (refresh feature) as far as I know but definitely so.