iMac Can Only be Booted in Safe Mode (Shift Key held down)

The install DVD that originally came with my iMac once booted the iMac but no longer. When I tested it today, I found it boots past the gray screen but it halts on a blue screen. I tried it twice and failed. I also tried CMD-R for good measure, but that too failed again.

As to my providing more details that YOU require, I am fully aware of what I am doing. The threads in this forum last longer than your interest or mine. I want people who come after to read all the details of what I went through. That includes details you have no interest in knowing but excludes my life story. I know there are times when I come across an old thread and I wish for more details than people provided, and that's why I do it for others. So please don't take my verbose explanations so personally. I simply have the habit of trying to answer most of the basic questions before they are asked.

I now have one last question for you. If the logic board or power supply is bad, how then does my iMac so very reliably boot into Safe Mode? That part doesn't make sense to me. Putting the question to you more specifically, what specifically does Safe Boot disable, such that it would be able to boot with a bad PSU and/or bad logic board?

Thank you for your time, Barney. I appreciate your kind assistance to date.

Barney, I greatly appreciate you help to date. I look forward to hearing what you find out.

In closing, I perhaps should reveal "one more thing"...

I live near Nagoya city in Japan, and my iMac was purchased here via the Apple online store in late 2009 along with AppleCare. In late 2010, I was still running Snow Leopard and every couple weeks or so my computer would lock up. I got in touch with Apple Support by phone (Apple in the US, to whom I could speak English), and after they walked me through many types of testing over the course of more than a week, they ultimately assigned me a day to take my iMac in to the Apple store in Nagoya, which is about a 1 hour drive from my home. The Apple store never did find the root cause of the problem, they never changed any hardware, and after a two week wait they returned it to me. I endured the lockups. Later, I installed Lion and was pleasantly surprised to see the regular lookups vanished! My computer locked up only rarely after that. Some time later, I updated to Mountain Lion. Still everything was working fine, although over time it "felt" as if my iMac was getting slower (lots of disk activity, apps taking longer to launch, etc.), but the computer was still very usable. Then, 5 months after my AppleCare expired, my daughter told me the computer locked up while she was browsing videos and photos in iPhoto. I powered down and found it wouldn't boot. Then I opened this thread in hopes of finding a solution.

What really has me concerned is that my AppleCare is expired. From what I've read on the net, it could cost me, in US dollars anyway, anywhere from $150-$1000, depending on whether one or more internal parts needs to be replaced. I also can't help but feel rather depressed about the fact that the root problem could have perhaps started back in 2010, but Apple never found anything in particular at that time.

Furthermore, the situation here in Japan is much more grim here than in the US. There in the US I see that you can get a few hundred dollars in cash by trading in your Mac for Apple store credit, under Apple's recycling program. But here in Japan, Apple's unfriendly recycling program terms dictate that you have to PAY to recycle your Mac. You get no credit whatsoever for the Apple Store here. Selling this iMac on EBAY is not an ideal an option for me due to the huge shipping expense from Japan to the US (the most likely buyers are in the US). And although Yahoo Auctions exists in Japan, most Japanese don't want machines for parts like they do in the US.

Sorry for being so verbose. I just wanted to present all the facts surrounding this case. I've been an Apple product buyer since my Mac 128k in 1984, but this is my first experience of having such a major and potentially costly problem.

All I want us a working computer so I and my family can use it in peace.

Thank you very much for your insight, Linc. I must admit such had crossed my mind. There were a few times over the last few months that I saw a few small "squares" in various places on the screen, but they went away when I moved some windows over them, so I didn't give them much thought. I would also like to add that after my computer stopped booting normally this week, I tried to boot from one of my FW 800 external drives which has Snow Leopard on it but not only did it fail to boot, I also saw some very unusual screen artifacts too. The strange thing is, when I run TechTool Pro's video test, it doesn't report a problem (albeit, I was only able to run TechTool Pro while booted in Safe Mode).

At this point, I would like to confirm this theory that the video card is the root cause of my troubles. How can I go about doing that without resorting to Safe Boot? More specifically, what video card related drivers or software can I disable manually in Mountain Lion so that I can reboot without the Shift key held down to verify if it will boot the desktop without freezing?

Thank you for your suggestion, but you only told me something I already know. I know full well that I could drive one hour to my local Apple store here in Japan, start the parking meter clock, wait a half hour to get service, take at least another half hour explaining things to the guy in Japanese, then perhaps be told they would need to confirm it over the next day or two, and then if they tell me a part needs replacing and if I agree to it, they will likely take a week to get it back to me, after I make another one hour trek to the store. Yes I already know that. But you did not answer my question directly, perhaps because you don't know?

I want to know how and what software I need to disable, pertaining to the video card, so I can verify myself if it is indeed the video card.

One other reason I have not yet made the long trek to my local Apple store is, if I can ascertain for a fact that a particular part is bad, in theory, I could purchase a brand-new replacement part on eBay, and fix the machine myself. (Yes, I am fully aware that such a repair would require me to remove the front glass.) Even if the EBAY route didn't cost me less then Apple would charge me, it still would allow me to continue using my computer, however barely usable it is right now in safe mode, while I waited for the part to arrive. But if I take it to an Apple store, they're going to have it for at least a week, and during that time, my entire family is without even a half-usable computer.

So my pointed question was one of tremendous practicality.

I look forward to your reply.

Thank you.

Linc, thank you for your reply, but honestly I was hoping for a verification method other than the Apple Hardware Test (and other than Safe Boot), which from what I understand can only be accessed by rebooting with the D key held down:

http://support.apple.com/kb/HT1883

I tried that many times, but holding down the D key does not take me to any kind of hardware test at all. (Which shouldn't be too much of a surprise, saying that I cannot even boot from the original Snow Leopard DVD that came with my iMac anymore.)

To be even more specific, what I was hoping is that one of you informed folks out there could tell me something like "go to this folder and remove such-and-such a file, and then reboot." If there is a video card driver that is causing something on the video card to be activated at boot time, then in theory disabling that software driver should allow the computer to boot, if indeed the video card alone is defective.

Thank you for that tip, Linc. I just tried your advice. I put the original OS X Install DVD in (while booted of the internal drive in Safe Mode), the I chose Restart, then I held down the D key. I heard the DVD being accessed for a couple minutes with the Apple logo and spinning spiked wheel visible, then the spinning spike wheel and apple logo vanished. The screen turned blue but then it turned gray, and then it gave me the space background image and asked me for a language choice! It then presented me with the Mac OS X Install dialog, but there was no Apple Hardware Test to be found. So strange as it may sound, I was unable to boot from this DVD in my last test, but this time I held down the D key and the DVD booted. Go figure.

Regardless of the lack of the Hardware Test I wanted, I proceeded to open Disk Utility (from that DVD) and formatted my internal HD. I then installed Snow Leopard on it and tried to reboot. To my delight it rebooted (no need for me to hold down Shift), and I proceeded to choose Country and do all the initial setup. After that it took me to the desktop. I then installed all the updates presented to me in Software Update. After that, I allowed it to do the install-and-reboot process. It booted until the space scene desktop pattern appeared, but nothing else (not even menubar) except the arrow cursor that was frozen in the upper left corner of the screen. I waited until drive activity stopped. Then I was able to move the arrow cursor around, but nothing else ever appeared.

I then was forced to powerdown the computer by pressing and holding the power button on the back left. I then booted it up and held down the Shift key. This time it booted to the desktop. It looks like I can access the App Store just fine in Safe Boot though, so should I proceed with installation this way?

NBAR, I am confused by what you are telling me: "Do not run the installation package on the CPU you are downloading from." Do you really mean to say CPU/Computer, or did you mean Hard Disk? Why wouldn't I just run the installer from my iMac's internal HD?

Futhermore...

NBAR, I just rebooted with CMD-OPT-R held down. It booted me right to the desktop, and very fast too. But I don't see anything different about this boot. It's just the normal Desktop. Am I booted into a "normal boot"? Or is this "safe boot"? Or is this something else. I cannot tell. But whatever it is, it booted me to the desktop without the need to hold down Shift.