HELP! My iMac wont respond to install disc or any commands

Question

I know I'm taking a trip in the "Way back" machine. But I'm pretty resourseful and haven't been able to find my problem. Either I need a Mac super genius or it’s something stupid simple that I’m overlooking.
Specs:
iMac G4 Serial# XXXXXXXX Sep. 2003 – July 2004
1.25GHZ/ 256MB/ 80GB 17” Screen
PowerPC 7445
History: I bought this used with the computer’s monitor backlight out. I could still barely see the sign-in page when I looked at a certain angle, so that was an indicator to me that the OS was working. So I replaced the monitor. At the same time because of owner exchange I had to replace the hard drive with a fully wiped blank one (Deskstar ATA/IDE). I purchased an install disc set 10.4.8, which according to Apple this computer is compatible with 10.2.3 thru10.5.8.
Problem: After reassembly, the replacement monitor works fine. But the system won’t respond to anything. All I get is the gray screen with the apple smiley face folder that alternates with a question mark. It won’t respond to the install disc, or any commands for that matter. Of course I double, triple, and quadruple checked my connections from reassmebling. Here’s what I’ve attempted, all ending up with the same screen display.
During power-up
C (…of     course to boot from the install disc. It just ejects the disc after about     30 seconds)
CMD-OPT-SHIFT-DEL
D (wont     respond to hardware test)
CMD-S     (won’t go into single user mode. It just goes to the same gray screen)
OPT (this     is the only way I get a different screen. It shows the recycle page symbol     and continue symbol. It will recycle the OPT process to stay on this     screen, but it won’t continue if I press that selection – nothing happens
I’ve reset the PRAM
I’ve tried different keyboards (all Apple)
I’ve tried plugging the keyboard into different USB slots
I’ve replaced the Hard Drive with yet another just in case. I’ve tried alternate jumper settings on the hard drive. The original wasset to “Cable”, so I set it to that. But I also tried “Master” jumper settings– no change in results. I can’t say for certain that I hear the DVD/CD drive spin up. But I figure even if I had a bad install disc or bad optical drive, I should still be able to get to the black screen single user mode, yes?  So I’m at my wits end. Can any of you Mac geniuses out there please help me? Thanks
<edited by Host>

Answer 1

Install discs are specific to the machine they came with.  You cannot use them on any other machine, so the ones you bought are useless.  Buy a retail black faced copy of either Tiger or Leopard and you should be able to boot your machine, you need to format the drive as Mac OS extended (Journaled) when you first boot from the new retail disc.
I have also asked that your serial number be removed, it's not a good idea to post it.