To restore you iBook/PowerBook to factory, you need the gray system disks supplied with your iBook/PowerBook
Inert disk 1 into the drive and old down 'C' key while rebooting. Then follow the instructions to restore or format and reinstall
If you don't have the restore disk supplied with your iBook/PowerBook then you would need to obtain these first.
The can be purchased from some online Mac spares vendors. Any good Mac spares company will direct you to which copy you would require.
Best of luck