help
Not sure why that is happening, but basically RPGMaker is looking for a certain audio file in the 'bgm' folder and not finding it for some reason.
Re-download a second copy of the Windows version of the game from this website. Go into that second copy's 'audio' —> 'bgm' folder. Find the file called 'RooftopsongL.ogg_.' Drag it into the 'bgm' folder of the game you are currently playing.