Can't install 10.5.4 on 10.4.11 why

Can someone help me, Please? I bought 10.5.4 on ebay and the disks look good, just like my other apple disk, but my IMAC 10.4.11 said "Can't install OS X on this computer. I have no idea why can someone help me. I want to install 10.5.4 so I can sync my IPAD with my mac now it seems I can't?

Thanks

spinnerlys said:

That's probably because they are grey restore DVD, which are model specific, so if you have an iMac 4,1 and the DVDs are for an iMac 4,2, then the DVDs won#t work. If you have an Intel Mac, you can buy the 29 USD Snow Leopard Upgrade DVD.

Or you have to get a REATIL version of Leopard.

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I wasn't aware that there was an Upgrade how do I get one? Have you any idea? Thanks for your response , I've been trying since yesterday including backing up my mac which started out as a small job. Very disappointed was hoping to sync my IPAD today.

Thanks again...

spinnerlys said:

As I don't know which country you reside in, I assume you live in Northern America or Western Europe, thus you can either go into any shop that sells Macs or order Snow Leopard online at the Apple Online Store, for 29 € / USD.

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I am in Austin, TX and they don't carry the software in the stores here it has to be ordered on line for 129 us dollars. Thanks!