Can my eMac

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Mac OS X Snow Leopard isn't compatible with PowerPC-based Macs, but as you said Mac OS X 10.5, you are referring to Leopard.

First, I need more information about your eMac, so open  > About this Mac, and check Processor and Memory. Here are the Leopard requirements > http://support.apple.com/kb/sp517

If you can upgrade, just get Leopard in Amazon or eBay because Apple doesn't sell Leopard, and upgrade. Make a backup of your files

Leopard requirements/10.5.x...

* Mac computer with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor

minimum system requirements

* 512MB of memory (I say 1.5GB for PPC at least, 2-3GB minimum for IntelMacs)

* DVD drive for installation

* 9GB of available disk space (I say 30GB at least)

Classic/OS9 Apps no longer supported.

May be available from Apple again???

https://discussions.apple.com/thread/4720126?tstart=0

Trouble is Apple no longer sells it, check eBay & such for the Retail version, not the Gray Discs... ???

http://www.ebay.com/sch/i.html?_nkw=mac+os+x+leopard+retail+10.5

There are workarounds if the 867MHz CPU is the only hangup...

http://sourceforge.net/projects/leopardassist/

http://lowendmac.com/osx/leopard/unsupported.html