You can upgrade direct to OS 10.5, skipping OS 10.3 & 10.4. Even though you have upgraded the processor speed, the bus speed on the AGP remains slow. So Leopard will be somewhat slow. Are you wanting to upgrade to Leopard so you can use iTunes 10.5, which is necessary for syncing an iPhone or iPad?
Mac OS X 10.5 Leopard installation system requirements
http://support.apple.com/kb/TA24950
Leopard is no longer available at the Apple Store but may be available by calling Apple Phone Sales @ 1-800-MY-APPLE (1-800-692-7753).
If you can't obtain a retail install DVD from Apple, look on eBay or Google the installer part numbers to possibly find at an on-line store. 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 😉
