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All Leopard discs are Universal. The operating system will run on any PowerPC 74xx, PowerPC 970, and Intel based Mac.
 
There are several G3 (PowerPC 750) based machines that can be upgraded with a G4 (PowerPC 74xx) processor. Although these computers started off as a G3, Leopard can be installed on them as long as they have a G4 processor. You don't even need to meet the required clock speed either to install Leopard.

There are several workarounds that range form editing the installer disc, just imaging the hard drive using ASR or NetRestore, cloning hard disks, or using Target Disk Mode to trick the installer that the target volume is on the faster Mac.

Not to mention that that machine specific grey discs are Universal and Drop-In Leopard DVD as well.

Keep in mind that system imaging to circumvent Leopard requirements is possible and legal. (Remember to have your licenses) Just don't expect much support from Apple even if they provide the tools and documentation to do so. If you don't have Mac OS X Server for Netboot/Install then NetRestore works in a pinch.
 
ah icic i want my emac to have leopard like my macbook cause its seems wierd using os 10.4 and os 10.5 but yea ithink i know what u mean cause i saw leopard on a emac g4 700mhz
 
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