cant over write axial sounds on FA06 or DS88 with new axial sounds

[mr music person]

im trying to overwrite preinstalled axial sounds on FA06 and DS88 but on loading the new axial sounds dont show up in display to select them. i dont know if there could be a fault with the USB's as had trouble updating there os on both keyboards with 1 make of USB but loaded with different brand USB but even these that work updateing there os still wont load the new axial sounds. also i was able to upload these axial sounds to my FA06 and DS88 with blank axial loaded (none) but its my freind with same 2 keyboards that have preloaded axial sounds that we want to replace with the same ones in mine but forvsome reason wont load. could it be something to do with the current, unwanted, axial sounds loaded and i dont know how to delete them unless loading in new axial sounds automaticly overwrite the unwanted axial sounds. so if any one can help with this it would be greatly appreaciated.