It sounds like a previous owner tried to install an Intel Mac version of OSX, as would happen if they used the gray system disks from a Mac made in 2006 or later. A PowerPC Mac like the eMac cannot read Intel code.
Did you get any original disks with the computer?
Few 4,4 eMacs will run any higher Mac OS that 10.4 Tiger well. That series has other limitations like a relatively slow system bus, a RAM limit of 1GB and only USB 1.1 ports. The probem is that Retail install Tiger disks are still in demand and can cost more than uded eMac.
You can use this link:
to find the exact specs of your eMac based on the serial number. Please do that and post what eMac series it says you have. That way we can get advice based on exact model details.
Good start. On the sticker where you found the serial number is the processor speed. In this example form that Apple page:
The line below the second bar code shows the example computer to have a 1.25gHz processor. See what yours has. That affects the OS upgrade path.
According to the MacTracker database, that modle shipped with OX 10.2.5 and 9.2.2 installed. I thik it was the last of the "dual-boot" eMacs---you could boot into either OSX or OS9 so you don't have to run OS9 program in Classic emulation. Some OS9 programs don't do well with Classic emulation, such as MS Office Mac 98.
You do not need OS9 to upgrade.
You RAM is maxed out--a good thing. And it's PC133, the "right stuff." THat model has a 100mHz system bus and some people mistaking use PC100 RAM and have trouble. FOr some reason Apple specs the RAM as 133-speed, and that seems to always work.
I've downloaded OS X 10.2.8 Jaguar
I'd not try a downloaded version. All are pirated and illegal, and many of the downloaded MacOS versions won't work at best or contain malware at worst. The are no official downlaods of any Mac OS other than OS10.7 and 10.8 which can be obtained only at the App Store.
OS 10.4.11 will run very well on that computer. If it's a 1Ghz processor it will technially run OS 10.5 Leopard but wil struggle with 1GB RAM, the slow system bus, and limited video hardware capabilities.
If you have a Mac User Group in your area, that is a good place to look for legal retail install versions of Tiger:
Sometimes schools will be willing to part with outdated system disks. Worth checking.
The big issue withTiger install disks is that most are on DVD. Fortunately, it look like all ATI Graphics eMacs had optical drives capable of reading DVDs.