Try inserting and booting from the disk that came with the MacBook.
Besides the installer there is a normal menu bar at the top of the screen. Look through the menus and find the item that allows you to select a start-up disc and select the normal Mac HD. This will re-bless your system, that is tell the computer where to find the information it needs to boot correctly.
Does not always work but is worth trying before going onto more drastic measures.
If that fails it is time to buy a copy of Alsoft's Disk Warrior.
Besides the installer there is a normal menu bar at the top of the screen. Look through the menus and find the item that allows you to select a start-up disc and select the normal Mac HD. This will re-bless your system, that is tell the computer where to find the information it needs to boot correctly.
Does not always work but is worth trying before going onto more drastic measures.
If that fails it is time to buy a copy of Alsoft's Disk Warrior.