my imac requires 10.7.5 to get the new itunes. I am only running 10.5.8

Choose About this Mac from the Apple menu and check the processor.

If it's a PowerPC Mac, it's already running the newest OS it can.

If it's a Core Duo Mac, click here, install the DVD, and run Software Update.

If it's a Core 2 Duo or better Mac, upgrade it as if it was a Core Duo Mac, and once done, if desired, open the Mac App Store and try downloading Yosemite. If you get told it's incompatible, go to the online Apple Store and order a download code for Lion 10.7.

Mac OS X 10.7 and newer don't support PowerPC software such as Microsoft Office 2004. If you upgrade the OS, back up the computer first.

A PowerPC or Core Duo Mac can't run the current version of iTunes.

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Get an external drive and then either use Time Machine or a product such as the Disk Utility, Carbon Copy Cloner, or SuperDuper to create a bootable clone.

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See the second and third paragraphs in my first post above.

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Wilks1 wrote:

is there an easy way to back up the Imac as i dont have external harddrives etc

You will need somewhere to back up to, an external HDD is the simplest method, get one.