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niall_mc Author

Level 1

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Bootcamp partition will not boot

hi there,

I am having an issue with my bootcamp partition on my MacBook.

The windows partition is showing up when I hold down the Option key on startup but it just brings a cursor saying:

A disk Read error occurred.

Press Ctrl+Alt+Del

When I boot into Mac OS X the partition and check Disk Utility the windows partition is greyed out and showing up as disk0s4

From reading other solutions on this site I thought it may be the GPT and the MBr but I am unsure how to fix it.

The results of my fdisk and gpt checks are:

sudo fdisk /dev/disk0

Disk: /dev/disk0 geometry: 60801/255/63 [976773168 sectors]

Signature: 0xAA55

Starting Ending

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

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

1: EE 0 0 2 - 25 127 14 [ 1 - 409639] <Unknown ID>

2: AF 25 127 15 - 1023 254 63 [ 409640 - 388671872] HFS+

3: AB 1023 254 63 - 1023 254 63 [ 389081512 - 1269536] Darwin Boot

*4: 07 1023 254 63 - 1023 254 63 [ 390352896 - 586420224] HPFS/QNX/AUX

sudo gpt -r -vv show disk0

Password:

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 388671872 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

389081512 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

390351048 1848

390352896 586420224 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

976773120 15

976773135 32 Sec GPT table

976773167 1 Sec GPT header

Any help would be appreciated.

MacBook Pro, Mac OS X (10.7.4)

Posted on Oct 7, 2015 11:11 PM

Best reply

Loner T

Level 9

59,471 points

Posted on Oct 8, 2015 3:26 PM

Please post the output of

sudo dd if=/dev/rdisk0s4 count=1 2>/dev/null | hexdump -C

View in context

61 replies

Loner T

Level 9

59,471 points

Oct 15, 2015 4:19 AM in response to niall_mc

Can you run Apple Hardware Test - Using Apple Hardware Test - Apple Support ? This may eliminate hardware issues.

niall_mc Author

Level 1

0 points

Oct 19, 2015 5:01 PM in response to Loner T

Hi Loner T,

I ran both hardware tests (short and long) and they both reported no issues.

Loner T

Level 9

59,471 points

Oct 19, 2015 5:24 PM in response to niall_mc

1. Was there a failed software installation attempt?

2. One option to consider is to re-install Windows on the same partition, which will save your old installation as Windows.old.

3. If there is any NTFS software which could have corrupted the NTFS partition, it can cause the problems reading the file system.

4. Was there any Virtualization software installed at any point in time?

5. Are you able to see the Bootcamp volume in OS X Finder?

niall_mc Author

Level 1

0 points

Oct 19, 2015 5:39 PM in response to Loner T

In reply to your questions:

1) I do not believe there was any failed software installation attempt

2) I haven't tried to reinstall windows - from my initial repair attempt it did not even recognise that there was a Windows installation on the machine

3) There was no NTFS software installed - the machine hadn't been booted to the Mac environment in over 2 months before the issue occurred.

4) There was no Virtualization software installed at any stage

5) The Bootcamp volume in does not appear OS X Finder - in fact this is all I require because it is only the data I am interested in. I am happy to blow away the Windows OS if I can recover the files.

Loner T

Level 9

59,471 points

Oct 19, 2015 6:02 PM in response to niall_mc

Download Testdisk from http://www.cgsecurity.org/wiki/TestDisk_Download and start a scan. There is an example in El Capitan has deleted my bootcamp windows partition with Testdisk setup and scanning. Let us check if we see any file structures which match Windows.

niall_mc Author

Level 1

0 points

Oct 19, 2015 6:44 PM in response to Loner T

Hi Loner T,

I downloaded and ran the Testdisk software. It was able to identify the MS Data partition but when I went to list the files it said 'Filesystem seems damaged'

Loner T

Level 9

59,471 points

Oct 19, 2015 7:01 PM in response to niall_mc

Using your Windows installer disk,

1. we should try and run chkdsk - https://technet.microsoft.com/en-us/magazine/ee872425.aspx

2. we can also run a Deeper Search in Testdisk.

#2 takes much longer than #1, but #1 may cause additional problems. #2 may be slow, but less damaging. My recommendation is #2. It may even take overnight.

niall_mc Author

Level 1

0 points

Oct 19, 2015 7:35 PM in response to Loner T

How do I do option #2?

Loner T

Level 9

59,471 points

Oct 19, 2015 7:38 PM in response to niall_mc

Do not Quit this screen, but hit Escape only once. You should go back one screen. select the MS Data and press Enter. You should see a Deeper Search option.

niall_mc Author

Level 1

0 points

Oct 21, 2015 6:48 PM in response to Loner T

Thanks Loner T,

I tried the Deeper Search option and it has been going for over 24 hours but it has not gotten past 0%.

Apologies for the image quality.

Loner T

Level 9

59,471 points

Oct 21, 2015 6:57 PM in response to niall_mc

It is supposed to be the ratio of the first number (sectors scanned) over the second number (total disk sectors). It is currently about 40%. You can ignore the 00%, which may be a calculation bug. 😉