Hi there, its my 1st time on this forum and i have a huge problem not quite sure where to post it...so a few weeks ago i attempted to install OS Lion on my imac intel core i3 and i think it didnt install properly and now the machine wont boot its stuck on grey startup screen with loading circle...so i did all of the test and in single user mode i get the following message *****file system could not be modified***** :/ root# fsck -fy ** /dev/rdisk0s2 ** root file system Executing fsck_hfs (version diskdev_cmds-491 .6~3) , ** checking journaled hfs plus volume. ** checking extents overflow file. ** checking catalogue file. Keys out of order (4, 11120) ** rebuilding catalogue B-tree. ** the volume macintosh HD could not be prepaired.