First, make sure the power adapter is plugged into the computer and into a functioning power outlet.
Your battery may need to be recharged.
Press the small button on the battery. One to four lights glow indicating the battery's level of charge.
If that doesn't work or if you hear a strange sound during startup:
If you recently installed additional memory, make sure that it is correctly installed.
Try removing the memory; if the computer starts up normally, the memory is not compatible with your computer.
If that doesn't work, reset the PMU according to the instructions listed in technical document 14449, "PowerBook and iBook: Resetting Power Management Unit (PMU)".
See the service and support information that came with your iBook for information on having your computer serviced.
This document contains information from the iBook User Manual.