Unable to boot up in bootcamp after installing Mountain Lion

I have exactly the same issue. The partition is still there, but for some reason ML is unable to select if for boot.

Here is how to solve it:

Check that the paretition is still there. It should show up on your desktop, otherwise check with disk utility.

If it is then:

0) If there is any essential data on it, copy the data to another drive, just in case the below doesn't work. Also make a backup of your OSX partition and data to be on the safe side. All should go smoothly, but we're talking computers, so pelase make sure you backup everything before.

1) Get Winclone from TwoCanoes (it's a great utility which will help you if you want to upgrade your HDD without having to reinstall Win)

2) Use Winclone (make sure it's the latest version, compatible with Mountain Lion, not one of the old free ones) to backup your Windows partition. You can back it up on your OS X partition, it's just one file. Ideally do it on an external HDD, it will be faster.

3) Use Bootcamp assistant to go back to one partition. Your Windows partition will be deleted, and you'll be back to have only one OSX partition taking the whole HDD

4) Restart

5) Use Bootcamp assistant to create a new Bootcamp partition. You can use the opportunity to change the size of the Windows partition to make it smaller or larger than it used to be. Winclone doesn't care about the size when it restores, so it doesn't have to match. Don't redownload the tools, and don't install Windows, it's not necessary. When Bootcamp assistant has created the BC partition, stop it before it installs windows and reboot.

6) Use Winclone to restore your bootcamp partition.

7) Restart, and hope for the best...

Let us know if that worked for you as it did for me.

Why not just try Windows 7 DVD and boot that, maybe you need to edit the BCD was all.

That could be a good first call, just make sure you have a backup of both partitions.

Also I thought if you have upgraded Paragon NTFS before ugrading SL to ML, the NTFS drivers of Paragon prevent you from selecting the Bootcamp partition to boot. You either have to select it for boot from the Parangon settings in the pref panel, or disable the Parangon drivers to make sure OS X is able to see the partition and therefore allow you to select it.

NTFS as startup disk is one thing but people use it to write and mount NTFS volumes to use under OS X.

Where does the "can't access NTFS partition" fit in? odd?

It might be odd, but that's the way Parangon NTFS works.

When it's enabled, OS X can't select the Bootcamp partition as a startup disk, that's why it provides an option in its own panel in the preferences to select Bootcamp and boot from it.

Of course it can read/write to/from any partition (including the Bootcamp). But OS X can't select BC to boot.

If you only use NTFS occasionally, you can disable the drivers and that way the usual control panel fromn OS X allows you to select the Bootcamp partition.

It just occured to me that the OP might have forgotten about this if (s)he uses Parangon NTFS.

yes I own and know that startup disk preferences change but it isn't really disabled, is it.

Option key works so it isn't blocking or preventing that either.

If someone forgot they would likely see Paragon though in the control panels.

Paragon sent out emails about 10.0 so that should trigger their memory!

There are no GUI tools on Mac OS X that will properly show you the disk's partition after Boot Camp has altered the disk. There are TWO partition tables after Boot Camp Assistant has created the partition for Windows, MBR and GPT. Disk Utility only shows you the GPT. And Disk Utility does not repair either partition table, it only repairs file systems (HFS+ and FAT).

I request that anyone who has upgraded to ML, who can no longer boot into Windows, go to Terminal and type the following read-only commands, which do not change any information on the disk, and post the results to the forum. No private data is in any of this, other than possibly the name of your hard drive.

sudo gpt -r -vv show disk0

sudo fdisk /dev/disk0

I'm curious what the GPT and MBR look like relative to one another, and if possibly the MBR has somehow been reset to a PMBR, which would explain the problem.

I'm having the exact same issue after doing in-place upgrade to ML with a Win8 Bootcamp partition. After upgrade, I no longer have the option to boot into Windows by holding option.

Here are the results of the commands as requested:

gpt show: disk0: mediasize=500107862016; sectorsize=512; blocks=976773168

gpt show: disk0: Suspicious MBR at sector 0

gpt show: disk0: Pri GPT at sector 1

gpt show: disk0: Sec GPT at sector 976773167

start size index contents

0 1 MBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 742851896 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

743261536 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

744531072 153633664

898164736 78608384 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

976773120 15

976773135 32 Sec GPT table

976773167 1 Sec GPT header

------

Signature: 0xAA55

Starting Ending

#: id cyl hd sec - cyl hd sec [ start - size]

------------------------------------------------------------------------

1: EE 1023 254 63 - 1023 254 63 [ 1 - 409639] <Unknown ID>

2: AF 1023 254 63 - 1023 254 63 [ 409640 - 742851896] HFS+

3: AB 1023 254 63 - 1023 254 63 [ 743261536 - 1269536] Darwin Boot

4: 0C 1023 254 63 - 1023 254 63 [ 898164736 - 78608384] Win95 FAT32L

I have no idea which version of OS X you have, but Disk Utility is perfectly able to display ALL the partions on a drive, including the bootcamp one, so my advice to use it to see if the partition is still there is perfectly valid.

True, it will not repair it if something is wrong, but it will allow you to check if it's there or not.

Anyway, I've given advice:

1) Check if Paragon NTFS is not preventing your bootcamp partition from showing up in the startup panel

2) Otherwise follow the procedure I initially outlined. It worked for me.

One thing though, Winclone can restore in a larger Bootcamp partition, but not a smaller one, so make sure if you use BC assistant to reformat that your new BC partition is the same size or larger, otherwise Winclone's restore will fail.

Signing off now as I don't understand all the pseudo advice going on here. It's a simple situation and it's easy to resolve if you follow the above.

I see two things. First, notice this fourth line from your GPT. It says ~73GB of disk space is not allocated to any partition, it's free space. Why?

40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 742851896 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

743261536 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

744531072 153633664

898164736 78608384 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

The good news is that partition 4 for Windows in the GPT and MBR have the same start - end sectors. However in the MBR no partition is marked bootable. One must be bootable and it's customary for Apple to mark the Windows partition bootable. I strongly suspect this is why Windows is not a boot option, and it's rather easy to fix.

4: 0C 1023 254 63 - 1023 254 63 [ 898164736 - 78608384] Win95 FAT32L

My suggestion is that you reclaim the missing free space before you proceed with MBR repair, but missing ~73GB of space isn't hurting anything. Try the following and report back:

diskutil list /dev/disk0

diskutil resizevolume /dev/disk0 limits

Again both are read-only commands and do not alter the disk information in any way.

@McManni

What I said is that Disk Utility only shows the partitions as described by the GPT. It does not inform you at all about the state of the MBR. It is a nearly useless tool for troubleshooting Boot Camp problems, a large percentage of which have to do with the MBR, not the GPT.

You admit you don't understand what's being discussed, yet you call it pseudo advice? Before you essentially call someone a liar on a public list, you might actually like to understand what's being discussed.

Not sure why the unclaimed disk space is there. I had originally upgraded the built-in hard drive to a 120Gb SSD, but due to space constraints and my frustration with Mac OS' unwillingness to show me where it was using disk space to effectively manage, I used winclone and moved to a 500Gb 7200 RPM hard disk. This is most likely where the funny partition information is coming from. Saying that though, after the upgrade, and while still on lion, everything was working perfectly for dual boot.

Here is the output from the commands you requested:

/dev/disk0

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *500.1 GB disk0

1: EFI 209.7 MB disk0s1

2: Apple_HFS Macintosh HD 380.3 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

4: Microsoft Basic Data 40.2 GB disk0s4

-------

Volume format does not support resizing

disk0s4 shows up in disk utility, but as mentioned, OSX can't do anything with it. I definitely lack the skills on OSX to repair the MBR on the windows partition, though it's a straight forward (read: familiar 🙂) process in windows. Very much appreciate the help, and goes a long way to show just how good the community can be for Apple.

My mistake, try this instead:

diskutil resizevolume /dev/disk0s2 limits

Result:

For device disk0s2 Macintosh HD:

Current size: 380.3 GB (380340170752 Bytes)

Minimum size: 163.7 GB (163734446080 Bytes)

Maximum size: 380.3 GB (380340170752 Bytes)