Ok, so I have a copy of an OS X 10.4 retail disk (Much much thanks to SticMAC!)

I have my Windows PC which I'm posting from, and my eMac (800MHz G4, 640MB RAM, was running 10.3) which I'm attempting to boot this DVD on, it has a DVD drive and it read it inside of OS X, but when I went to reboot I held C, it showed a gray screen, ejected disk, i put the disk back in still holding C, showed another grey screen the a purple folder came up and flashed a ? for a small second then shows the finder icon.

So I read an article which says this means it cant find the boot drive and to hold option to select what to boot from, so I did it and now it's asking for a password (DAMN EDUCATIONAL FACILITIES!) which I don't know, i've tried admin, administrator, password, NOTHING, apple, emac, Bryanston (Name of the school printed on the bottom of the eMac) but no luck.

I seriously need some assistance with this asap, sorry to sound rude but I do.

Thanks

I had to look for this one.

Try changing out the RAM to where there is an absolutely different amount of it in there. Use new RAM if need be. Then start up while holding command-option-p-r (it's a stretch, I know). Continue to press those keys until you hear three ADDITIONAL bongs (so you'll hear four total) and then let go.