IMac will not boot Mac OS from any device, just Windows XP

Hi there,

Since a while now my IMac will not boot MacOS anymore. It started with an occaisional "hangup" on the grey startup screen, but that was usually resolved after a power reset.
The strange thing is that it will startup from the Windows XP partition no problem.
I can also access the Mac-partition from another Mac using the "Firewire" option. I ran the diskcheck and no errors were reported.
This enabled me to make a full backup of the complete disk (both a disk-image and specific user doc's) and reformat the Mac partition.
The problem is that the IMac will not boot Mac-OS from any other mac-device either: I tried the original OS DVD and an external USB-bootdrive; but the system just keeps rebooting after 10 to 15 seconds of "grey screen".
When holding the "Alt"key I can see all boot devices on the screen; the only one that actually works is the Windows-boot disk.
This makes it an quit nice Windows XP pc, but that's not why I bought it (except for the fact that the sound-device doesn't work, but I do get the old fashioned "chime" after powerup).

I also used the "PRAM" reset procedure a couple of times: no change.

Hope that anyone can tell me if there are any more options before I take it to the shop.

many thanks in advance,

Joannes Paanakker
Amsterdam (NL)

What happens if you set Mac OS as the startup disc in the Windows bootcamp utility and reboot?

Thanks for your response

I tried that; no change: systems keeps rebooting after showing the gray screen for aprox. 11 seconds.

JP

A PRAM reset should have resolved that problem. I suspect you may have a bad hard drive or some severe corruption in the boot sector. Have you tried to wipe the drive and reinstall? You seem to have made a backup of your OS X partition but you will also need to backup the WinXP partition.

If your WinXP partition is formatted to NTFS you can probably use WinClone to make a backup image and restore. If it's formatted to FAT-32 it will likely not work.

I guess I'll have to try that in the end, but there's a reason why I haven't yet:
When in "T"mode (firewired to the other mac) the system will boot OK from that Mac partition.
This gives reason to believe that it is not a harddiskbootsector problem (if so it would not boot from either system, right?).
The fact that the IMac also failes to boot from DVD or any other external device supports that theory.
Is there any other reason why a system will not boot the Mac OS?
So now I have an Imac that will only start up Windows, but when I want to use the Mac partition I have to connect it to another Mac and can't use the fantastic screen (the ohter mac is macmini with a standard TFTscreen).

My worry is that after wiping/formatting/fixing/exchanging the harddisk, the problem will still resurface.....

So now I have an Imac that will only start up Windows, but when I want to use the Mac partition I have to connect it to another Mac and can't use the fantastic screen (the ohter mac is macmini with a standard TFTscreen).

Click to expand...

I have seen machines boot from the Windows partition and unable to boot from OS X; replacing the hard drive and reinstalling resolved the problem. Booting in Target mode does not mean your hard drive is OK since you're really booting from the host computer.

And again, not being able to boot from the disk could likewise be the result of a defective hard drive. If it were a MB or MBP, removing the hard drive could prove it one way or the other. However, removing the hard drive from an iMac is a more difficult task and not recommended unless you have to swap the drive out.

And then again, you could be correct in that your hard drive is OK and something else is amiss. You have some choices to make.

OK, so I whiped the disk in the end and reformatted to 1 Mac partition. Than I restored the disk image from the external disk and after two hours I could finally test the result.
I disconnected all disks and restarted the Imac and... after the "chime" the apple logo appeared and than the light grey screen turned dark grey from the top (this was new so I thought to be on the right track) and the message appeared telling me to restart the machine in four languages: English, French, German and something like Arabic or Cyrillic or whatever.
Restarting the system resulted in that same message though; this is what we Dutch call: "getting out of the the rain into the drip". IOW: the situation changed but did not improve really.

I reformatted the disk one more time without restoring anything and restarted the system: this resulted in the appearance of a folder logo with an flashing question mark (quit logical,since there was no systemsoftware on the disk).
Another restart with the original OS-DVD brought me back to square one: the system keeps rebooting after 15 ot 20 seconds.....

So, any other ideas?

thanks,

JP

It sure looks like you have a failed hard drive. The "restart in four languages" is known as a kernel panic which is generally indicative of a hardware problem.

What seems to verify that is when you attempted to boot with the install DVD and went back into the restart loop. If you decide to change out that hard drive yourself, you can view the instructions to do so (in English) at iFixit: The free repair manual.

OK, I changed the harddrive following the instructions.
Indeed not as complicated as I thought, as long as you use the right tools.
Removing the window-plate is easier than expected: I used two simple suction cups that hold up my towels in the kitchen.

But still no change: system keeps rebooting after 10 seconds, regardless what bootdevice I choose.

So it must be another hardware issue, but what puzzles me really is: why will the system only boot a Windows XP OS and no Mac OS (regardless the device chosen)?

Hope anyone has other suggestions, I'm afraid the people in the shop will tell me to just buy a new one or replace the logicboard or something drastic..

I fixed it. The solution was: buy "Snow Loepard".
the screen would show a UNIX like trap just before rebooting, and I had to make a video with my iPhone to see what it said. After throwing that text into the Apple helpdesk it came up with the fact that my iMac would not boot with an "old" Mac-OS.
I will not try to understand why it worked up until it didn't; the only thing I did was install dual boot at one time so I guess the system got confused at one of the updates.
Anyway, it was no hardware problem in the end, but I do have a harddisk with double capacity now.

cheers,

JP

Certainly a strange one. Why your machine worked and booted before is a bit of a mystery. That was what threw us off into thinking the hard drive was at fault.

Anyway, I'm glad you resolved it. You now have two hard drives instead of one and some experience on how to get inside an iMac.