Recently my MacBook has been acting up quite a bit. A few days ago Firefox kept crashing so I shut the computer down. When I started it back up, the light blue screen showed up, with a continous beeping noise. It made about two beeps, paused, then beeped twice again. I turned it off and turned it on several times till it booted up properly. It's happened again to me today. My Firefox crashed several times so I shut my computer down and the same beeping noise played, only no matter how much I switch it on and off it refuses to start up. Before Firefox crashed it erased my history and I was unable to use to back button (it was greyed out). I have some really important files on there, is there a way to back up all my files and/or fix the problem so I can continue using it? It used to make the startup sound on the light blue screen then make the beeps, but now the screen is grey and just beeps... if I hold the power button down for a while, the little light with rapidly blink on and off for about two seconds then goes back to normal.... what's wrong with it?