Ibook g4 help

I need some searious help with my I book. Every time I go to boot up the apple screen with the little circle on the bottom that indicates loading comes up but when It comes to the next screen it flashes then nothing but blue. Every once n' a while it will load all the way then freeze before even a minute passes. I have tryed the unplug the battery and hold the power button to reset back to factory but it hasent worked. I dont have the os x disk because I bought It from a guy that was kind of a tweeker. any help or clues would be great, and thank you in advance.