Welcome to the Apple Support Communities
See if your Mac is supported > http://support.apple.com/kb/sp575 Buy Snow Leopard > http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard Then, make a backup, insert the DVD and upgrade. Finally, go to > Software Update and install the most recent version.
You need to install Mac OS X 10.6.8 to run iTunes 10.7.
Download iTunes 10.7 here: iTunes 10.7
To upgrade from OS X 10.5.8, you must first buy Snow Leopard on DVD disc. It is not available to download from any legitimate source.
Elsewhere: call the phone number in the Apple Online Store
Apple's price is $19.99 or £14.00.
Make sure your system meets Snow Leopard's requirements:
Mac OS X 10.6 "Snow Leopard" System Requirements
To install Snow Leopard for the first time, you must have a Mac with:
- An Intel processor
- An internal or external DVD drive, or DVD or CD Sharing
- At least 1 GB of memory (RAM) (additional RAM is recommended)
- A built-in display or a display connected to an Apple-supplied video card supported by your computer
- At least 5 GB of disk space available, or 7 GB of disk space if you install the developer tools
After you install Snow Leopard you can decide if you want to upgrade OS X to the latest version, Mountain Lion. Mountain Lion is available in the Mac App Store, which is available to you after upgrading to Snow Leopard.