Dead iBook

Over 6 months I had trouble with my Lime iBook. until finally it has become completely unbootable. While using the iBook it would suddenly just stop like it had been turned off. Resetting the power management chip and the pram worked for a few times this happened - and the machine would be all right for a month or so; but this last time it shut itself down even resetting the power management chip won't cause it to rebook. Have tested the power input and battery are all fine. The screen is black and the drive does not spin up. The caps lock light will show, indicating power is getting to the machine; sometime when pressing the start button the CD draw opens. Any Ideas would be welcome??