Newbie needing help.

Hi I just got a computer to try out that has os 9.2.2 on it. I got it to get my feet wet I guess as far as mac goes. It is an old Imac with a 333 processer. It was working fine for a couple days then today it just shuts off for no reason. I started it back up and it shuts off again. I let it sit and it will start up and I can use it for a little while then shuts down again. I do know alot about pc's both hardware and software but again only new to mac. I was thinking it is a heat problem the way it was acting but figured I should ask before I dig in lol. What should I look for? how long should the imac be turned off before it is safe to start messing with the inside? from looking on the internet I see that there is possibly a log file that may tell what is shutting the computer down, where would I find this? Is there any program that I can put on the comp that could help diagnose like heat problems, hard drive problems, etc? I would take it to a mac repair shop but unfortunatly I am the only computer repair shop within a 4 hours drive.

Welcome to the right side! You have a couple of issues, one is that the 333 MHz iMacs are now eight years old. It does sound like a heat shut down. Unplug it, tap the power button to discharge any stray million volts of electricity and crack it open.
Lots of patience, tiny screws, more patience, stay organized and you will find the logic board packed with cat hair, paper lint, missing socks, etc. Carefully blow it clean with compressed air, or slurp it clean with a vacuum. Carefully. I do not know of any System 9 temperature programs, there are several in OS X. It might work, and at least you will get personally acquainted with the innards.

I wouldn't recommend cracking it open as a first step. I'd get canned air or, preferably, if you have an air compressor or know someone that does, or you know someone with a machine shop or a woodworking shop or you're friends with your mechanic or something, blow it out with that. If there's anything wrong with the circuit in the CRT that's set up to bleed residual electricity out after powering the machine off, you could very easily kill yourself poking around under the hood of that machine if you don't know what you're doing.

Thanks for the quick replys I cracked it open and there wasent much dust that I could see but cleaned what was there and when I found out where the processor was I checked it and as far as I can tell the thermal compound had dried up so I removed it and put new stuff on it and it hasent shut off since. (fingers crossed)