Hello! My wife's iMac won't boot. OSX 10.6 Snow Leopard. It began by chiming then displaying a folder with question mark. Now it chimes and displays an apple with the spinning flower-thingy but doesn't go any further. I can option-boot to a Linux live-CD then ssh in to invoke ddrescue on the 250GB on-board HDD (/dev/sda) to a 1TB Toshiba HDD (/dev/sdb). After running the three level recommended ddrescue routine ddrescue log shows 100 errors totaling 60kb. The cloned disk is recognized without complaint on my Dell laptop. I used the Plugable Lay-Flat dock. For anyone working on these vintage machines, here's an awesome resource.[/edit] Reading the threads I'm concerned that the CPU fan isn't working and overheating may be another problem I have, so I'll be looking at that once I open the case. Before I do that, what other operations or diagnostics would you recommend I perform on /dev/sda before I remove it? Should I happen to get it to boot, what further should I do before removing it and replacing the HDD? My concern is that while it appears I got a pretty good clone, If the problem bits are in the boot sector, it may not be quite good enough. I'd like to take the case apart and reassemble it (only) once. (How) can I compare the contents of the respective booting info before I make the swap? I have another new 1TB HDD available I can use if you have other suggestions. My plan is to install the OWC 6GB RAM and 1TB HDD; verify that the fan is working correctly and upgrade to Mountain Lion. Do you see problems with that plan? If I get a bootable system I would plan to use parted to move the partition backup table to the end of the HDD so the whole 1TB would be recognized. I don't think I ever got an installer disk (Tiger 10.4) with the machine. Do you disagree? I've looked but didn't find it, but I just thought of another possible location. I'll look again. I upgraded to Leopard and Snow Leopard online as I recall. There's an Apple Store nearby which is an AASP. Another option is I could stop everything right now where it is and take it over there. I can always use the HDDs elsewhere. I might even be able to return the RAM. Thanks for taking a look and for any suggestions you have! [edit 4/12/16] Since writing this I opened the case and replaced the original disk /dev/sda with the ddrescue cloned disk /dev/sdb. Attempting to boot. It chimes. All four LEDs light. The apple logo appears, the spinner spins for about 3 minutes then the machine halts and the screen goes black. Holding Shift does not appear to trigger Safe Mode. After about 3 minutes then the machine halts and the screen goes black. This is Snow Leopard. I don't think it includes Command+R, at least I didn't try that. Reset PRAM Ctrl+Option+P+R appeared to run as expected; chimed twice; but after about 3 minutes then the machine halts and the screen goes black. I then tried booting in verbose mode (Cmd+V). I will try to post that output here so you can see it. [edit 4/12/17] It occurs to me it may be the PRAM battery. I'll change that and see what happens.