I have a key on my keyboard that brings it up, and I hit all of the time accidentally.
It's a proprietary Logitech Calculator key, and their own program doesn't let you remap it.
This seems to be a hard problem that many people are failing at solving – the google results were awful. Apparently if you munge the EXE file windows will just fix it against your will.
Best Answer
The answer is Applocker.