iMac will not complete any startup

I have 2 drives inside my 2008 iMac. A week ago it froze, and when I after an hour got tired and restarted it the progress bar stopped at about 20% and would not continue.

I restarted from my second internal drive with the same result. I even restarted from en external drive with the same result.

I checked the 4 LEDs, and they are all on. The drives have been checked and are declared OK.

What can be causing this? (I contacted Apple but they told me that they don't keep spare parts more than 5 years, so no help there!)

I got a new iMac, but would like to keep my old one just the same.

Do you think you know what is happening?

There is the original HD (1 TB) and in place of the CD drive i have a "Crusial CT480M500SSD1 2.5-inch 480GB M500 SATA 6Gb/s" that has been the main drive for the last 2 years.

The external HD I also tried to restart from is a Drobo partion (500 GB) with a CCC copy of the SSD on it.

I have also restarted from either drive's Recovery disk.

I can also mension that I can see 6 or 7 small pale blue "waves" across the dark gray Apple logo.

I restarted using "S", "cmd-S", "cmd-V", "cmd-PR" and probably some others I have forgotten. In verbose mode the process stopps after it mounts the Recovery drives and the dismounts them - that is when I start from a normal HD.

Ask me more if you need.