I have sony vaio vgn fs215s laptop. When I use it with battery alone it makes a constant "bi" noise that gets louder on more power consuming tasks. Sometimes on startup the screen goes black before xp logo. Then i hear the windows startup sound but sill black screen. I bypassed the xp logo (via msconfig) and it gets me all the way ok but the noise is still there. There is no problem when the laptop is plugged to a socket. What do you think is the problem and how do i fix it (how much money)? Thanks a lot.