Minecraft "game already running"

Ok so I have had this problem for over 4 months, every week or so I decide to try again to look for a fix. There is just no way to fix this. I have reinstalled the entire game 10 times, deleting the %appdata% files and reinstalling. I have changed in the game directory, as apparently that was the cause, and yet this message still comes up. Oh but you may think, just press start anyway. When you do that, the launcher crashes. There is no fix to this, and I might as well buy a new account. If I were to contact Mojang they would tell me to do everything I have already tried. Now, please if any of you here have any ideas that could actually WORK, I would be so so grateful.