Unable to re-install 10.4 onto original flat-panel iMac

Question

After 10.4.7 update trashed my original iMac (another long story!!) I now find that re-installing 10.4 from full install disk fails repeatedly about two thirds through.
I have tried the following ;
Used disk utilities to completely erase hard disk overwriting with 0's
Run hardware diagnostics successfully - no faults detected
Tried re-installing original 10.1 software that came with computer.. again this fails about two thirds of the way through.
Have also used diskwarrior to repair disk.
After having tried all this about 10 times.. i'm completely at a loss what to do next..
Help !!!!
System in question is "old" 15" flat screen IMac 700 Mhz PPC4 512 Mb RAM 40 Gbyte HD that had been rock solid until 10.4.7 update......
Macbook 1.8 GHz 512 Mb   Mac OS X (10.4.6)   iMac PPC4 700 MHz 512 Mb

Answer 1

I have to ask if you have not ever used places like Apple Downloads, MacUpdate or VersionTracker to find and download software? or Google? Should probably throw http://wikipedia.org/ - just to be fair, too
I think a bootable FireWire backup is much more useful in the long term - while .Mac etc can help with some personal files, it won't let you book your Mac.
usually Apple wants you to remove 3rd party memory and peripherals or upgrades to diagnose a problem. Same goes for OS X, always good to have an "Apple only" clean install that you can rely on; have backed up (DMGs work fine too), as well as a "working backup" of your system.
Practice makes perfect. no one learns without making mistakes along the way. Which is why there is 'testing' your backup and recovery plans hopefully before there is a disaster. Although there is always the FEMAs and lots of bad examples of how not to do things.
http://www.memtestosx.org/