Boot issue w/ iMac24, display issues

This is my first post so thanks for any help you can provide me. I've not touched an apple product since the IIe so it's been quite some time for me. Anyway, I have an Imac24 (A1225) that recently has ceased to boot. It would just get the grey screen w/ the apple logo and the rotating dial would eventually freeze. I'll list what troubleshooting steps I've done to save some time below. I've been researching before running out of options and asking for some help and have read there is a hardware test that can be performed from recovery or (app cd 2). However I have the install disk (OS 10.6) and one application cd, nothing stating application cd 2 so perhaps I am missing this?

Steps I've taken
1. Booted to recovery partition, OS, safe boot, from installation CD but hangs before it gets there
2. performed a verbose boot and It hangs in one of two spots.
3. Put a different HDD in and tried a clean install from install cd but it also hangs.
4. Booted from each RAM chip separately to attempt to isolate a bad RAM chip.
5. Reset PRAM/VRAM and SMC
6. It WILL boot to single user mode but I'm clueless as to what to do from the command line of a MAC


Note: when it does hang on the install cd the video gets a bit messed up at the top 1/8th of the screen or so if that makes any difference. Also noticed once the screen turned green while booting from installation cd which makes me suspect the video card. Just not sure that the video card would cause the lack of boot issue or not.

Verbose boot stop points:
Sandbox: authd(69) deny file-write-create /private/var/db/mds/system/mdsDirectory.db.sh-9f6a2a6f-g4UcrT
or
SMC::smcReadKeyAction ERROR: smcReadData8 failed for key BEMB (kSMCKeyNotFound)

Thanks again and I hope I've done some diagnostics steps to help you guys point me in the correct direction..

Dave

Intell said:

Excellent diagnostic steps. I concur that it is likely a bad video card or a failing logicboard.

Click to expand...

Thanks, aside from just putting in a known good video card, is there a way to determine if it is the system board or the video card that is at fault? Can you tell me where I can find this hardware test that is mentioned? I believe the OS on this iMac is 10.6 so the d at boot will not work correct? I've now read the hardware test is on the application disk 2 or the install cd. As stated I see an application cd (doesn't mention a cd number and isn't bootable) and the install cd which of course hangs so if the HW test is on there I'm screened anyway. I just want to get this working to learn my way around mac's a bit more.

BTW, I've already disassembled this thing and played about with it, reseating everything and checking the thermal grease on the video card in hopes it was an overheating issue but no luck. I'm a die hard pc guy but the engineering and design behind apple products is by and far the best I've seen in a computer product. Kudos to apple on R&D.

Dave