Please help us out and tell us where you are so we can tell you where to look. It is questions like this that are the reason Apple wisely elected to give us a "Geographic Location" field in our profiles.
I can give you a word of caution: Older Mac OS version like 10.4 and 10.4 are in high demand, so have unfortunately attracted criminal opportunists. The are NO legal or safe downloads of Mac System Install packages for OS10.5 and 10.5. All are illegal; many contain malware or just don't work.
You must also avoid gray-colored system restore disks--they are intended for only one model Mac and may not have the software components your hardware requires.
A legitimate Tiger retail install disk is black with a big silver/gray "X" on it. It WILL NOT say "Update." Also be aware that most Tiger install packages come on DVDs and some earlier eMacs did not ship with DVD-capable drives.
A last and sad note: because of demand, legit Mac OS install disks today will likely cost more than a used eMac is worth.
To use Mac OS X 10.4 Tiger, your Macintosh needs:
* A PowerPC G3, G4, or G5 processor
* Built-in FireWire
* At least 256 MB of RAM (I recommend 1GB minimum)
* DVD drive (DVD-ROM), Combo (CD-RW/DVD-ROM) or SuperDrive (DVD-R) for installation
* At least 3 GB of free disk space; 4 GB if you install the XCode 2 Developer Tools (I recommend 20GB minimum)
See Tom's, (Texas Mac Man), great info on where/how to find/get Tiger...
Or Ali Brown's great info on where/how to find/get Tiger...
* 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.
Trouble is Apple no longer sells it, check eBay & such for the Retail version, not the Gray Discs...
There are workarounds if the 867MHz CPU is the only hangup...
https://discussions.apple.com/docs/DOC-2541 should help you locate what you are looking for on 10.4 in terms of what the disk looks like, and possible software.
The 700 Mhz eMac can't run 10.5 or later without some serious alternations with a third party software called LeopardAssist. And even then it may not support everything supported by 10.5 on PowerPCs, and certainly nothing that is Intel only. It also does not have a system specific disk that will work with it that is as new as 10.4. The last 700 Mhz eMac shipped May 6, 2003, when 10.2.6 was just released. However there were no 10.2 retail discs that would run on it, only the 10.2 eMac.Some eMacs older than August 1, 2002 came also with a Mac OS 9.2.2 eMac installer, but no retail 9.2.1 would install on it. After that point only the restore eMac installer discs could install Mac OS 9 on the eMac with their restore installer programs.