iMac Makes Clicking Sound, Won't Start Up

Hello, I'm new to this forum. Unfortunately today I've encountered some problems with my iMac.I'll start by giving some specs.

20'' iMac G5 Intel

2 gigs of RAM, installed at the Apple Store the day of purchase.

OS- Leopard

The computer is passed it's one year warranty.

250GB LaCie External Hard drive,Ethernet Cable, USB to iPhone dock were plugged in at time of incident.

At the time of the incident I was running Firefox, iChat, and iTunes. I walked away from the computer and I heard tapping noise. Thinking it was someone at my window I walked over to it. I then began to hear a loud clicking noise coming from the iMac. The noise seemed to be growing in intensity so I reached behind the computer and turned it off. After letting it sit for a few minutes I attempted to turn it back on. I heard some noise and thought it would boot up as usual but instead I was greeted with a black screen. I waited and nothing.The white light in front of the computer is on.

In order to fix the problem I've tried:
Letting it sit for about ten minutes.
Unplugging it the plugging it back in.
Removing everything plugged into it.(aside from the power cord of course)
Trying a different outlet.
Hitting the volume button in an effort to see if maybe the computer was fine but the display was broken.
Calling Apple technical support.
Holding in command,option,p,r while turning it on.

If anyone has any suggestions it would be very helpful. My computer is very important for school as I'm in TV/Film and need Final Cut Pro.

First thought would be the HDD failed. Can you boot from the Install disk or the external?
Try Disk Utility from the install disk. (repair disk) If it is the HDD, it should let you know.
Also, the Apple Hardware test.

I just tried that and I don't think it worked, at least I can't tell, my screen is entirely off and I can't tell what's going on?

Ahhh...Try reseting the SMC first.

Have a look at these, too. Doesn't sound like fun though...
http://docs.info.apple.com/article.html?artnum=300908
http://docs.info.apple.com/article.html?artnum=86815

I think I found what I was looking for earlier.
http://docs.info.apple.com/article.html?artnum=302181

I tried reseting the SMC, unfortunately to no avail.
Also I purchased my iMac after the window for the program you showed me. Thanks a lot for all of your help so far though, I really appreciate it.

Sorry your 1st post is not going so well.
I would try the diagnostic I posted earlier. Either it's a power problem or the video card went bad. (usually)
Can you try an external monitor?

You said you tried reseting the PRAM?

Not at the moment. I may have an opportunity to try that tomorrow though. i'm currently removing and reinstalling the memory, i've tried every step in this tutorial http://docs.info.apple.com/article.html?artnum=303138

Wow, the night keeps getting better, according to the apple website my warranty expired yesterday.

That usually would be funny.
You did say you contacted them earlier. Maybe that will help. It's definately not going to hurt. I'd give them a call again.
Did you try the diagnostic yet?

Update:

I scheduled an appointment at the genius bar at my local Apple store. The genius there tried to fix it but was unsuccessful. My warranty expired two days prior to my visit but he said it wasn't a problem. They shipped it away and told me it would be finished and available for pickup in 3-5 days. I received a phone call 4 days later telling me to come pick it up. When I arrived I was shocked to find the repairs and new parts would have cost $899.00 and instead it was free. All customer service was amazing. This entire experience has reinforced my overall love for the apple brand. When my iphone broke 6 weeks ago I had a replacement shipped to my house in 2 days. Thank you Soulwar for all of your help.