Install CD/DVD crash every time

Question

Install cd/dvd all crash --
-------- the short version ----
Both are Sawtooth-- all install disks are retail -- tried opt key selection --
g4 400, had os9, install from boot cd - x2 then x3 then x4.
upgraded cpu and vid card
30 days later : slow start = 3 minutes
try to reinstall osx4, boot disk crashes. osx2 & osx3 install disks crash.
Attempted following procedures, repeatedly and in different combinations:
reset nvram, remove pram batt, change ata cables, change cd--drive, run memtest on ram, Removed upgrades = Restore machine to original configuration & reset nvram, remove pram batt.
Check PSU, seems weak, at 200 w max, test shows momentary drops below specs
Also remove hds, disconnect zip, put slave hd on same cable with master cd-drive. tried 3 different cd-drives, NONE of these things have resulted in booting from the cd-drive.
Get 2nd g4 450, 236 PSU, no hds. put hd from g4 400 into it and try to boot from install = crash. Boots to the hd with x4.10 on it, Install TechToolPro4 and make an “edisk”. firewire edisk boots - hd boots- cd crashes.
IF ONE machine was bonkers I would blame the machine, but two NO, especially the g4 450 is pristine - makes me wonder if it has been used more than a few hours EVER.
Rework g4 400 - install old 20 gig hd with osx3 on it, it boots, try boot from cd, cd boots up BUT no hd is loaded, in disk utility no drives show up. Change the ata cable and try again, now boot cd attempt locks up. Still boots to hd x3.
Here's a “hmmm” at one crash I found this line in command line = “ expected / previous boot version not the same” (I don't remember verbatim)
I thought removing the pram batt cleared that from logic board mem.
Back at the office I had a PM9600 running osx3.9 (with xlr8 patch) and had to clear the power (pram batt remove procedure) to boot back to os9, but it worked and had no problem of it. why do both of these g4s fail to boot to cd/dvd? Currently (used to originally install osx) Nec 2500 cd/dvd drive and the new Pioneer 112D, new cables, cleared pram and nvram AND reformatted drive from edrive (TTP4 emergency drive).
I have run out of ideas, unless there is some firmware command (other than nvram)
Is this an electronics engineer question?
Any one else ever had this situation?
thanks for help
K
please remember the already attempted diagnostic attempts.
Is it possible that osx4 added something to boot-rom, or firmware?
That an install disk will not boot just makes no sense to me at all.

Answer 1

Since it was two machines, and alot of hardware, and install disks, I had to stop and restart my thinking.
I put both machines back to stock, made a list of requirements for each bit of hardware, and inspected the disks very closely.
The original problem may/probably result of flaky powersupply and nVdia card combination. Disks wont boot because nVida requires X 10.4.5 to allow boot.
All the swapping parts and drives only shifted conflicts, didnt remove them.
Put New unfromatted hd in G4-400 and (0S9 no boot, OS X2 boot but no install) OSX 3 boots and installs, try to upgrade to OSX4 and crashes, look at disk again, skuff marks = I used a disk cleaner device that spins on the disk, supposed to clean it, but I "cleaned it" 10 times in succession.
Reboot and install took, so those small skuffs were part of the problem.
Went to the G4-450 and installed OSX 3 and upgrade to OSX 4.
Now one step at a time upgrade hardware, and
#1 keep a running written log of everything done to the machine.
#2 get an install disk with osx 4.6
#3 remember the lessons learned ---