Just noticed the 10.3.x
So we know more about it...
At the Apple Icon at top left>About this Mac, then click on More Info, then click on Hardware> and report this upto but not including the Serial#...
Model Name: eMac
Model Identifier: PowerMac6,4
Processor Name: PowerPC G4 (1.2)
Processor Speed: 1.42 GHz
Number Of CPUs: 1
L2 Cache (per CPU): 512 KB
Memory: 2 GB
Bus Speed: 167 MHz
Boot ROM Version: 4.9.2f1
Hmmm, I find no Firmware updtes needed for eMacs which is one thing that can prevent Target mode...
Have you done a PRAM reset, CMD+Option+p+r...
Does it boot into Open Firmware with CMD+Option+o+f ?
reset-nvram (press Enter)
set-defaults (press Enter)
reset-all (press Enter)
Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...
I have never done a Firmware update, as when I bought it, ran Software Update, all updates for Panther/eMac had already been installed.
I'm not quite sure about PRAM battery, as I live in New Zealand and am not really sure where to get them here. Pressing either of those key combos does nothing, the Mac loads Panther as if nothing happened.
Recap on start keys:
FireWire TDM: NO
Safe Boot: YES
PRAM Reset: NO
Open Firmware: NO
All key combos that don't work simply result in the eMac ignoring the key combos and standard-booting Mac OS X.
As described in original question, it is a wired keyboard.
I would, however, like to make sure that it is PRAM battery at fault.
There isn't a way to check the level in the battery is there? I don't want to replace a perfectly good battery, and for all I know, it could have been replaced last month, I only bought the thing 3 weeks ago.
I'm sure that would work if I actually HAD a voltmeter.
As from what I have read in http://support.apple.com/kb/HT1242 Time, volume, startup disk, DVD drive region code, Console info etc. don't change upon reboot, so something tells me it isn't the battery. Even after I left it unplugged for 2 hours when I cleaned the case down (schoolkids!)