my mac is 10.4.11. what's the easiest way to upgrade to lion 10.5?

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If you use an iPhone 5, the iTunes version that support the iPhone 5 needs Mac OS X 10.6.8 or later, so you have to upgrade to Mac OS X Snow Leopard. First, check if your computer 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, open  > Software Update and install the most recent version

Since you're using an Intel Mac, skip it and buy Mac OS X 10.6.

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