iMac not booting... help!

[MonkeyJamboree]

i already posted a similar topic on this, but i thought i'd ask something else in another place... i have a Bondi revB iMac that won't boot from CD or HDD at all. I used MacDisk for pc, and another program for PC to check out the file and dir structure, and everything LOOKS okay... though i couldnt tell what was supposed to be the default system or whatever that the drive is supposed to boot from. i've tried just about every suggestion i have come across to get this iMac booting again... (it originally had 8.6, i tried to upgrade hdd, it didnt like it, now won't boot and only gives me ? and flashing) i've tried resetting nvram, pram, replacing the ide cable, double- triple- and quadruple-checking the drive jumper settings... tried burning multiple backups of different OS versions, and still nothing will boot. tried booting with no drives, then plugging in and booting again. nothing. tried holding shift, tried holding option, tried to boot from open firmware. still the same thing. only on one occasion can i get the iMac to do something different: when booting a backed-up OS9 disc, it goes to a plain grey screen and stays there. in all cases, the cd drive winds down after a long time, when it's not in use.
anyway, i'm getting off-topic here... is there any way to copy files back onto a drive using a pc so that a mac will boot from it? do i have to specify the system folder on the HDD or do i do that in Open Firmware? i still have all the files from 8.6 that was on there, but for some reason the iMac doesn't want to boot it after switching out the HDD then back in again... any suggestions? (right now, i'd just be happy with 8.6...)