Ok, this is an interesting problem. So, I was using my MPB (Nov 2007) and CyberDuck kept freezing, so I decided to restart. On restart, mail refused to quit so I had to forcequit it. The rest of the shutdown was fine. Then it tried to start up again. The apple logo appeared along with the spinning cog thing underneath it. This screen stayed and never went, so I held down the power button and tried again - the same. I then loaded the 10.5 upgrade disk and when it had loaded, it did the usual "Checking for previous versions of OS X". It then came back with the error saying that OS X 10.4 or later was not installed on my MPB (This is the point that I actually got worried). I went into disk utility and it listed the HD but there was no partition. I then went to terminal and entered 'Volumes', the only one listed was the install DVD. I restarted and tried again; the same. I waited a while and tried again just for the sake of it and the Macintosh HD actually appeared in terminal. I have not tried booting again or going back to Disk Utility because at the moment I am using terminal to copy all files that I have changed since making my last backup (on the 27th of April) to my external drive - at the moment it is copying my 30GB aperture library so it may take a long time. Does anyone have any ideas why the whole partition would just dissapear and yet when booting OS X, it didn't say an equivilent to the windows "Operating sytem not found" error? And why, stranger still, it would just appear again in terminal. I guess I had better wait until I have copied all files and try booting again. At least with Time Machine, I will have most of my files. I have not dropped my laptop or given it any other shocks, it has been working fine all day until just before I restarted it. AJT.