I have an older PowerBook G4 with OS X 10.4.11, it has the 1.5ghz PowerPC G4 processor. How do I upgrade to 10.5 OS X? it has the

Buy it from a source such as Amazon or eBay.

(73578)

Mac OS X 10.5 Leopard installation system requirements

http://support.apple.com/kb/TA24950

Look on eBay or Google the installer part numbers to possibly find at an on-line store. Expect to pay about $100. Here's what to look for:

MB427Z/A Leopard 10.5.1 install DVD

MB576Z/A Leopard 10.5.4 install DVD

MB021Z/A Leopard 10.5.6 install DVD (single user)

MB022Z/A Leopard 10.5.6 install DVD (5-user family pack)

Installing Mac OS X 10.5 Leopard

http://support.apple.com/kb/HT1544

Mac OS X 10.5 Leopard Installation and Setup Guide

http://manuals.info.apple.com/en/leopard_install-setup.pdf

After you install the base 10.5, download & install the 10.5.8 combo update at http://support.apple.com/downloads/Mac_OS_X_10_5_8_Combo_Update

The DVD should look like this

Caution - Leopard does not support classic mode. So, if you currently open OS 9 apps in classic mode, you won't be able to do this if you upgrade to Leopard.

 Cheers, Tom 😉