I installed 10.5.5 from a black multi-license disk. iBook is a 1.2GHz processor (?) and has 1.5GB upgraded RAM. HD is pretty fullonly around 5GB unused after install. It booted fine the first 4 or 5 times. Now it is either "off"orange light on charge cord, caps lock light doesn't come on when you hit the keyor "on"charge cord light is green, caps lock light goes on/off when you hit the key, power light is doing the "bright-dark" cycle. BUT, there's no boot. That is, it comes on, but doesn't boot. And, once it's on, you can turn it off with the power button. Hold the power key down to start it up & you get a whirr/clicking like it's going to boot, screen flickers with backlight, but no start sound, no apple screen, no spinning gear, & it seems to be going to sleep. Have tried: resetting PRAM, but don't know if it's doing anything b/c no startup chime to measure when I should hold the keys; holding power button to open in firmwareno result whatsoever; booting in "safe" mode, again no effect. Whatever I do, the best result is the one where it makes the whirring/fan blowing/HD clicking sounds, but never goes any further. Alot of what I'm doing seems to have no effect at all. Ideas?