Hi everyone I would really appreciate some urgent help here. My son was round yesterday and was using my MB Air. He was listening to some music off some site and who knows what else he did. I booted up this morning and all seemed fine. I walked away for 5 mins and when I came back there was a message on the screen saying it needed to reboot. As I couldn't do anything it had to be reboote d. All it went to was a folder with a question mark. I have some stuff on an external Hard Drive (not a lot and I have never tried it) and the snow Leopard installation disk, however I do not have the original disk that came with the laptop 18 months or so ago. I have searches various threads but nothing seems to work for me. The only thing that has sort of worked is booting with the external CD drive with the Snow Leopard CD in it. I can go into the Disk Utility and it shows the external DVD drive plus a 79.68 Gb drive (which I presume is the Hard Drive) which is not mounted.) I have tried a repair but it says it can't repair this disk. Can any one please help?