My powerbook g4 wont boot

If you are getting to the blue screen, you are well through the boot process, but it is hanging on loading MacOS.

Have you tried Safe Boot (holding the shift key down at boot) to see if you can get to your desktop or the login window? If you get that far, you can maybe check your system log in the Console utility for a clue or maybe do a permission repair in Disk Utility to see if you can clear things up.

Which specific PowerBook G4 are we talking about here?

Disconnect all peripherals from your computer.

Press the Power Button and immediately press and hold down the Command and the S keys as the machine starts up. This boots you into Single-user mode and you should see white text appear on the screen.

When you see the # Command prompt, type /sbin/fsck-fy and hit the Return.

Now sit back & let your computer do its thing. This should take approximately 15 minutes or so. Depending on how messed up your computer is. Just be patient.

If and when you see the message File System was modified repeat the steps above again & again until you hopefully see the message "no problems were found." When that happens type reboot and hit Return again.

If these steps do not work then boot from your install disc to repair disk. To use the Install Mac OS X disc, insert the disc, and restart your computer while holding down the C key as it starts up.

Select your language.

Once on the desktop, select Utility in the menu bar.

Select Disk Utility.

Select the disk or volume in the list of disks and volumes, and then click First Aid.

Click Repair Disk.

On the single-user mode, you should first write-enable the root volume with the following command

/sbin/mount -uw / <cr>

then go ahead with running fsck.

/sbin/fsck -fy / <cr>

Space between commands and switches very important

OK, you did write-enable the root volume with

/sbin/mount -uw / <cr>

didn't you? That last forward slash is very important, as it means "the root volume."

That being said, if you did write-enable before running fsck, then you need something stronger than fsck, which would (among other things) be DiscWarrior from Alsoft which is much more aggressive in fixing boot directory problems.