somewhere in the settings of bsplayer will be an option to always check if it is the default player and to make it so if it is not. you have to unselect this option to keep the program from doing this every time is starts up. same as web browsers if you have more than one. each one will check if it's the default and harass you to change this until you tell it to stop checking and just be happy it's installed.
start skimming the options until you find it or google search it and i'm sure there is a walk through out there somewhere.