If you're using an *eMac* and trying to install Snow Leopard 10.6 there is no way on earth it will work.
An eMac is a PowerPC RISC processor.
Snow Leopard will not run on a PPC machine.
You need to have an Intel CPU for that.
To have a working OS on your computer, you need Leopard OS X 10.5 or earlier.
Yes. Your best bet to find it is on ebay.
You want the FULL retail 10.5 installer that comes on a disk with the 'space' background and the big black X on it. (it looks identical to the retail Snow Leopard disk)
The grey colored disks are *computer specific* for the machines they came with, and NO G4 eMac shipped with Leopard 10.5 as Apple had already changed over to Intel CPU's by the time 10.5 came out..
NO grey-colored Leopard OS disk will work with the eMac.
Black-colored Leopard OS disk is what you need.
There are 'family packs' that are selling with iLife and iWork, but you can find single-pack OS disks much cheaper.
You will like using Leopard, it has all the new security and networking stuff and your eMac will look and act simillar to a new Mac running 10.6 and 10.7.