Use a firewire cable to connect your old Powerbook to the new one. This won't hurt either of them.
With your new Powerbook on and logged in, boot up your old powerbook while holding down the 'T' key on it. This will cause it to mount on your new machine as a hard drive. From there, just transfer the files over.
Comments
With your new Powerbook on and logged in, boot up your old powerbook while holding down the 'T' key on it. This will cause it to mount on your new machine as a hard drive. From there, just transfer the files over.