Original iMac crashes and doesn't start

Question

I have the original iMac from like 4 years ago, I do not have the original software disc, I have newer mac's with the install disc, theses are intel, dueo disc.
I get the happy Mac chime when I start, I did run the original hardwear tester CD, everything is fine (it did take a long time on the memory test)
computer hardly ever starts when it does it crashes soon after. (dark grey dialogue box in center of screen)
Could this have anything to do with installing newer intel core dueo disc after completly erasing the original system softeware ?
Could it be that the memory has gone bad ? I've reset pram, switched and removed accessories, etc etc.

Answer 1

First, you should identify your iMac model more precisely. The "original" iMac had a translucent blue-green case with a CRT display inside, but it does not sound your model is THAT old, especially if it was new when you got it "4 years ago."
Here is a list of all the iMac models.
http://www.everymac.com/systems/apple/imac/index-imac.html
If you can identify your iMac model precisely, or at least more closely, you will get more helpful responses. One key distinction is whether it has a PowerPC (such as "G5") processor, or an Intel processor. You are posting in the category for the iMac G5 (PowerPC not Intel).