Just delete it from the startup folder, but it will reappear once you restart the computer or run the signage player again. The best way to solve this is to uninstall the player and have a dedicated computer to serve as the player.
Articles Tagged: stop
Cannot Stop SignagePlayer it keeps on reloading
Go to the task manager (ctrl+alt+delete) and choose start task manager, Click on Processes and look for Cmd.exe, SignageController.exe and SignagePlayer.exe and end that. This will close SignagePlayer and allow you to do what you want with it.