IvyMD: Which OS X 10.4 discs do you have that won't run
in your computer AND what are the specs of the computer?
A retail disc set should work in the computer you have.
Not a set intended for a 'specific computer' however...
An install/restore disc from another computer won't work.
{There was a way to install Tiger from retail DVD into a
Mac that does not have a combo or super-drive; and
in those instances, a second computer with the drive
and a FireWire cable for Target Disk Mode may work.
Other options with different hardware may be required.}
And a simple 'upgrade disc' that won't boot the computer
would leave you without vital disk tools or full reinstall
capabilities; nor the basic ability to repair the 10.4 install.
The database at MacTracker you can get for free will say
what versions of OS X are supported in various Macs.
http://mactracker.ca Note: lowendmac.com often lists places
with a weekly or monthly price/availability of older OS X discs.
Tiger can be a bit costly now in some cases hard to find, but
also see MacTracker; it tells you what later Macs use 10.5.
Even where Leopard may be supported in the last eMac
models, it may be too much for the older graphic processor
and need a RAM upgrade in most cases if not already max'd.
In any event...
Good luck & happy computing! 🙂
{ edited 2x }