Using the Mac OS X disk you have for your iBook, incert and hold down 'C' during boot.
When it loads up the menu, click utilities and then Disk Utility. (Menu at the top)
In Disk Utility select your macintosh hard drive from the left.
In the right menu, select disk repair. Once the disk repair has finished, restart your iBook without the dsk in the drive.
It should loads into Mac OS normally.
Best of luck