in order to check and fix error for booting in Mc OS: see below solutions
• "Press X during startup" = Force Mac OS X startup
• "Press Option-Command-Shift-Delete during startup" = Bypass primary startup volume and seek a different startup volume (such as a CD or external disk)
• "Press C during startup" = Start up from a CD that has a system folder
• "Press N during startup" = Attempt to start up from a compatible network server (NetBoot)
• "Press T during startup" = Start up in FireWire Target Disk mode
• "Press Shift during startup" = start up in Safe Boot mode and temporarily disable login items and non-essential kernel extension files (Mac OS X 10.2 and later)
• "Press Command-V during startup" = Start up in Verbose mode
• "Press Command-S during startup" = Start up in Single-User mode
if you have no choice for this then, please use Mac DVD an reinstall is best solution.
have fun
