Can no longer boot into Mac OS

Hello,

I have lost the ability to boot into Mac OS X.

This is a 2009 (?, used) MacBook Pro running OS 10.10, 11, or 12 (sorry) and Windows 10. (There are probably going to be a lot of palm-hits-forehead moments reading this post.) I've had it partitioned for four or five years. Yesterday I found I was no longer able to boot into Mac OS X at all.

The computer has always booted into Windows by default for reasons I can't fathom, but plays the Mac startup sound and presents the Mac blank grey screen before starting to boot into Windows. Naturally, I just hold Option to get into OS X. This no longer works. Neither Option nor any of the other startup key combinations (Cmd-R ...) I've tried has any effect, I'm not presented with a choice of drives to boot from, and the computer boots into Windows from the Mac blank screen as if I'd let it be without pressing Option.

Windows auto-updated yesterday and I didn't download, install, or do anything else unusual, so I believe the update must have broken this functionality somehow. I tried to revert the updates, but Windows wouldn't give me the option to revert three of them, and reverting the others didn't have any effect.

I tried resetting Windows (deleting programs, but not files), but that had no effect.

I plugged in an Apple USB keyboard to see if the keyboard was malfunctioning, but that had no effect.

I can't boot from an install disk because my disk drive is broken (has been since I bought it used). I don't own an external disk drive and am too broke to buy one (seriously). If the best option involves buying an external disk drive, please still let me know so I can follow up on that when I have money again.

This is not a perfect dual-boot installation. I partitioned my drive (with Windows 7) after Boot Camp was no longer supported, and had to follow some online instructions to access the utility. Because of either this or a failure to follow instructions, Windows has always run a little wonkily--as I said, it decided it would be the default OS, I can't change the screen brightness, the speakers sometimes can't find their drivers, the microphone often doesn't work. But I've never had a problem as severe as being locked out of Mac OS before.

Thank you for any insight you're able to provide.

THH

Boot and immediately after the chime hold the Option key. Does the OS X partition come up?

If so proceed, and when in OS X go to System Preferences > Startup Disk and highlight the OSX drive to boot into OS X. Start saving your pennies as it is nine years old and in a poor state by the sound of things.

That's the problem, holding the Option key has no effect; the computer continues to Windows without displaying the different partitions.

Sounds like you are out of options. There is a limit to what you can do to fix a computer when the only resource you have is the same device. The computer itself is old and as you have said there are a number of intermittent functional losses. You need a diagnostic device other than the device itself. Another Mac would do or a bootable OSX installer on either USB HD or Thumb Drive. This really comes down to friends and family when cash is limited. Even if you can get your hands of one of the above it may just confirm that your HD is full of bad blocks or corrupted beyond repair. In any case you stand to lose data. Backup what you can now.
It maybe possible to repair the HD but in most cases I can think of that would entail erasing the disk.

Next, you could try, NVRAM and SMC resets?

https://support.apple.com/en-us/HT204063
https://support.apple.com/en-us/HT201295

Try the NVRAM reset, and then test if fixed. If not, try the SMC reset. I will add, on separate occasions, I had to perform these multiple times, to get the desired fix.

@ Rod Sprague: Thanks. We do have other Macs around; I'll try booting from one of them. Not that I really know, but I'm not sure that the hard drive is corrupted, as I am able to read and copy all my files using HFSExplorer.

@ ferrarr: Thanks. I have tried the NVRAM reset a few times to no effect. I'll try the SMC reset.

Thanks, guys.

Hmm, my previous post seems not to have taken. Thanks for the suggestions, guys. Rod Sprague, I'm currently following up on your suggestions of backing up (via HFSExplorer) and trying to borrow a FireWire cable to connect another Mac. ferrarr, I have tried the NVRAM reset a few times; I will try the SMC reset as well.

I take it you need this device and can't afford to replace it?

TheHumanHydra said:

I have lost the ability to boot into Mac OS X.

Click to expand...

One question. Did you purchase this computer used 4-5 years ago...it was setup as it is now when you purchased it...and you haven't made any modifications since? Or did you do the hard drive partitioning, macOS install, and Windows install?

Back to the problem. One possible longshot idea. Do you know how full the macOS partition is. If it's completely full...that could be an issue. Also not being able to boot into the Recovery Partition is not a good sign. It should always be able to do this if things were installed correctly & there are no hard drive issues.

- Nick

Rod Sprague, alas, that's correct. I'm looking for work right now and won't be able to afford a new machine until I have it. As long as the Windows partition still functions, I can do everything I need to, though. If I can't ever get into Mac again I guess I'll look into giving the whole hard drive over to Windows. pigoo, yeah, I bought it used a number of years ago, but did the partition and Windows installation myself. Obviously I've upgraded the Mac OS a number of times, and I upgraded Windows 7 to 10. The Mac partition is fairly, but I don't think completely, full.