Imac shuts down randomly

Power issues can be related to the SMC. You already did part of the following procedure, but try following the instructions precisely to see if it makes a difference.

http://docs.info.apple.com/article.html?artnum=303446

So you unplugged everything like it says, waited at least 15 seconds, etc... like it says to do?

If it happens faster when using something processor-intensive, it could be heat related. Check the iMac to ensure vents are not blocked with dust (or anything else). Do you hear a fan come on before it shuts down?

Did you install this SMC firmware update already?

http://www.apple.com/support/downloads/imacearly2006smcfirmwareupdate.html

To Contact Apple for Support and Service in Mexico call: 001-866-676-5682

http://www.apple.com/support/contact/phone_contacts.html

Or use this Apple On-Line service request!

https://selfsolve.apple.com/GetWarranty.do

I have a lot of discussion about this on my thread:

http://discussions.apple.com/thread.jspa?threadID=1088454

Does the clicking sound like electrical noise or mechanical noise? The power cable on mine became loose on my 17" Early 2006 and I had to remove the logic board and re-seat it. It is not for the faint of heart, but it fixed my issue. I hypothesize it is from vibration over time or poor assembly.

I went through an ordeal to find this out, but if you decide to get it serviced, have them remove the logic board and check the underside for a possible loose DC-in connection if all else fails. They will try and get you to replace the power supply and motherboard at first (and charge you a ton of $) so ask them during their "diagnosis" to check for this.

If you decide to ditch the machine and want me to take a look at it I will be more than glad to, just let me know. After having to troubleshoot mine I kinda miss it! Call me crazy!

It may be the Video card-Sound Stupid & irrevelant but it is worth a try to get it looked at.

That makes some sense, since you seemed to experience the shutdowns more when playing games.

What were those tools you mentioned? I'd like to try them myself...

Just wanted to let you know that I bought an imac intel alum Nov. last year and a few weeks later this happened to my computer with fan noise. I finally decided to bring it over the store and get it repaired. It took me THREE times to finally get a new computer! I literally cried to the tech telling him that I worked so hard to buy this expensive computer to get a BROKEN one! The second time that I brought it in, one tech told me "well if it breaks again we will fix it". The third time I told him that I didnt spent over a thousand dollars to get a broken computer that I had to come every month to get it repaired?!?! and that how many times I have to bring it in to finally get a new one?!?! They understood my point and with no fuss they replaced it with a brand new one AND they transferred all my data. I am so HAPPY now!!! On another note: the last time I tried to rebooted the screen would not pass the white screen with the apple logo, it was stuck and I freaked out!!! I thought that I have lost all my data!!!! PLEASE everyone, if you have experienced any problem like this TAKE IT TO THE STORE! The guy was telling me that the problem was uncommon (YEAH RIGHT- I GUESS THEY ARE TOO BUSY THEY CANT COME TO CHECK OUT THE BOARDS!) If you take your computers to the store with this problem then it will NOT be an uncommon problem and you might get a new comp! GOOD LUCK!!!

To be fair, Apple sells millions of Macs a year (over 2,000,000 during the December 2008 quarter alone). If even half-of-one-percent have problems like yours, that's thousands of people who may potentially have a reason to be here on the "BOARDS." And not that many customers would bother to post on the forum just to report that everything is working great.

But I'd like to officially report that I bought a refurb iMac recently, and it's working perfectly.