I wasn't 100% sure if this topic was appropriate for this area, but this seemed the closest.

I have had a mac that someone gave me a while back. It was having "problems" they said and they didn't want it anymore.
I finally got around to plugging it up and seeing what I could learn about it and hopefully fix it. I have some os x cds that were given to me with it that said to press and hold c or d at startup for either install or diagnostics.
Neither key seems to yield anything. The mac just boots up to the gray screen with the apple on it. Are there any recommendations, is this machine scrap, or am I holding a button incorrectly.

I believe it to be a power mac g5, but I'm not certain.

I was unable to figure anything more about the mackintosh. I hope someone can point me to a good place to get help. I've asked in a few other places, but no responses yet.

I have looked up and tested other boot up keys, but they don't work. The only thing that appears to be working is, if I hold the primary mouse button or I hold the eject button on the keyboard the cd drive will eject.