iMac install

[volvoguy]

I can't seem to get my iMac to boot the install disc at all. Is there
some secret that I don't know about besides holding down "C" while
booting?

These are my system details:

Rev.D 333Mhz Grape iMac
256Mb RAM
20Gb Seagate HDD
Tray-load CDROM

I don't have a burner in the iMac so I'm burning the disc on my PC
with Nero. I thought an ISO file was an ISO file but maybe I'm wrong.
I've tried with and without closing the disc when burning.

Any thoughts or is this system just beyond what is supported? 

Thanks!

Aaron