I have a G4 iBook that until today has run fine. Today in the middle of a blog post, the screen turned a dark grey color and the computer was unresponsive. I was able to shut it down with the power button, but the next time I started it, the grey screen came back after a few minutes. I shut down and restarted several times and was able to save the most important data to a disk, during the brief moments when it was booting up. Then finally, it started up and ran fine for several hours, before the screen went to grey again. Now the screen is black. It won't shut down or start up and the fan just runs. Is the hard drive dying? what do you think?