Eliminating Quick Scan from executing.

How do I completely eliminate Quick Scan from running? This scan runs at the most inappropriate times, like in the middle of a game, or when I'm online, and really slows things down!

 

I have checked the box 'Do not schedule' on the Custom Scan page but the scan still runs. I cannot check the 'Delete' box because it is grayed out.

 

Any help would be greatly appreciated.

 

Quick scan.jpg