Imac problems

Well I haven't been able to get any help with my PC problems lately, I don't know if its because I have learned all of the easy stuff, and my hardware problems are more and more complex, but this should be an easy one for a Mac guy.
Problem : IMAC 500mhz. I bought it to learn OS X, it doesn't always boot, if its been sitting for a while and you press the power button is lights up and then shuts off, if I press and hold the button sometimes it lights up and stays lit up but nothing else happens. If I open it up and press the board reset button, play with the ram, pull out the cmos battery and a few other things it will start and run flawlessly for a few days. I've tried narrowing it down one thing at a time, but just messing with the ram, the reset button, and the cmos battery has no effect on it, I need to do some combination of all three.

Ideas?

 

Is your Imac used? Maybe the motherboard is fried. Also, I think you will have better luck posting the Mac subforum.

 

oh there is a mac sub forum, eh damn I thought hardware is hardware... ok um no mobo is fine, it just booted again. I didn't mess with it this time, it just worked.

 

This is an old an out of place thread but I wanted to update the solution I found for my imac booting problem. The steel (aluminum) shell under the plastic one was grounding out in some way and that was what caused it to have problems. I removed the shell and never had another failed boot. The same could be repaired with insolating material around its base. Again if this is in the wrong place and you can move it to where it needs to be please do. I googled until my fingers bled and only got cooked mobo answers.