The fix you tried is supposed to do exactly that. WMP should only be starting in Now Playing if the target contains that line "
Task:NowPlaying". This is one of those absolutely bizarre issues that crops up when you
know it shouldn't be happening, but nonetheless it does. I recently had it myself (see my first posts on this forum where I was having trouble with a partition. My computer wouldn't even let me complete step one.)
I have no further suggestions I'm afraid