You need either a 2nd partition to boot from, or a boot disk with Disk Utility on it. First answer is to try and repair the disk. If that fails (likely based on your description) then it's time for an Archive Install.
Note: hangup followed by boot failure can be caused by a hard drive failure, but the answer is much the same. Install new HD, then boot from install disk and install a fresh copy of the OS.
So I'd say you need to find the install disks for each computer. Or a Tiger retail install disk that works on both. A Leopard disk will reject your iBook G3. If your iBook has a CD drive, then you either need CD retail install disks (Jaguar, Panther, Tiger option), or a USB drive big enough to take an OSX install from the G5.