Currently Being ModeratedMay 29, 2013 8:01 AM (in response to ellenmsch)
Depends the age of the Powerbook, and your operating system.
Powerbook G4 867 Mhz or higher can run Mac OS X 10.5 to 10.5.8, but do not support Classic when doing so.
Depending on the age, they may support booting into Mac OS 9 while maintaining Mac OS X 10.5.8.
This link explains what versions of iTunes work with what Mac OS X versions.
A newer version for 10.5 only is here.
Older versions may be found here.