Problems with re-install.

Question

Firstly, I know hardly anything about Macs yet am quite proficient with PC's.
My mother's old Imac (G4 800 MHz) was running very slowly and had hung during "tech tool" drive tests for several months. I decided that I might as well back it up, wipe the disc and re-install.
The machine had been purchased with OSX 10.2 and had been upgraded to 10.3.X and ultimately 10.3.9
I backed up every file I could to a remote drive.
I then took the 10.3.x upgrade CD 1 and booted from it, selected disc utility and deleted the hard drive. Naturally (being an upgrade only)the ensuing install failed as there was no previous version to upgrade.
I then tried to boot from the gray 10.2 install disk 1. The machine did not recognise the disc. Guessing that something from the later version was blocking further installation of the earlier version, I opened the machine, and both re-formatted the hard drive on a PC and removed the battery to zero the BIOS (or whatever the very similar thing is called). I reset PRAM and NVRAM as well.
Still no joy booting from either the OS install disc or the software restore discs that came with the machine. Machine however happily booted from the 10.3 upgrade disc, the Ibook 10.4.x install disc, the apple hardware check disc and the tech tool disc.
At this stage I assumed there to be a fault on the install disc media.
Finding a mate who had an old Emac running 10.1, I was amazed that the discs work fine.
It seems I should have been more careful which software I used to delete the hard drive with. Surely there is a work around or back track? I seem to be stuck in a never ending loop.
Any suggestions would be great - tearing my few remaining strands of hair out

Answer 1

You stated that you were able to boot the machine with a Tiger (10.4) installer disc. Why not, then, install Tiger which is a better choice than Panther? If the iMac has at least 256 MBs of RAM it should run Tiger (but it would be better to max out the memory in the machine.)
Be sure you repartition and reformat the drive because your PC format is not usable by OS X. You can do the following:
Extended Hard Drive Preparation
1. Boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger or Leopard.)
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID (for Intel Macs) or APM (for PPC Macs) then click on the OK button. Click on the Partition button and wait until the process has completed.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.