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I backed up all important data prior to formatting the C: drive, but I cannot read the backup drive after reinstalling Windows. More details provided after the screenshots.

Additionally

As you can see, there are three physical disks in this system:
- 1TB System (C:) drive.
- 0.5TB basic MBR disk (D:) for general storage.
- 3TB basic disk with a single 3TB GPT partition (E:) for general storage.

Since the D: drive did not have enough free space, I used the 3TB GPT E: drive to backup everything I needed from the C: drive before formatting.

The 3TB E: drive was initialized as GPT and formatted as NTFS using the disk management GUI from Windows 7 Ultimate x86 while it was still installed. However, after formatting the C: drive and installing Windows 8 Enterprise x64, I get the "GPT Protective Partition" problem shown in the screenshot above. Almost all options in the right-click menus are greyed out, so I don't even know where to begin.

I've found a lot of interesting ideas on the internet, but nothing that really fits my situation.

If my understanding is correct, the 2TB "Protective" partition is a fake partition that the GPT system emulates. The idea is, if your system cannot read GPT, and can only read MBR, it will see this fake 2TB MBR partition, so you don't accidentally format it thinking it's empty - hence "protective."

This leads me to the main questions:
- Why would Windows 8 Enterprise x64 be unable to read GPT drives, while Windows 7 Ultimate x86 had no problems whatsoever creating and using this partition?
- How can I get Windows 8 Enterprise x64 to read this drive properly as GPT, so I can recover the backup data stored there?

EDIT:
Here's the GPT and MPR data for the disk, produced by gdisk. The fact that it says all 2.7 TB are "free sectors" worries me a bit, as the disk should be quite full of stored files. Prior to re-installing Windows, this drive functioned flawlessly as a GPT disk with a single 2.7 TB basic non-boot partition.

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Is this a Mac system? –  allquixotic Jan 14 '13 at 21:16
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@Giffyguy: He means the drive, did it come from a Mac system? –  Tom Wijsman Jan 14 '13 at 21:24
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Stupid idea 1: Boot up a Linux Live CD (e.g. Ubuntu 12.10) and see if you can mount the full volume as GPT there. Stupid idea 2: Try Linux (e.g. Ubuntu 12.10) in a VirtualBox or VMware virtual machine, giving physical access of the HDD over to the guest, and see if you can mount it there. Either way, the next step is to copy off the data, and manually reformat the drive clean and reinitialize the GPT partition table. –  allquixotic Jan 14 '13 at 21:27
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Have you performed a full shutdown of Win8 after installing it, instead of the normal hybrid boot thing where it hibernates the kernel? Can you try shutdown /s /t 0 and see if anything changes after a reboot? –  Karan Jan 14 '13 at 22:18
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It's likely that there's something wrong with the protective partition, or perhaps with the GPT data structures, that's causing Windows to try to read the MBR data structures rather than the GPT data structures. Try downloading the Windows version of gdisk (sourceforge.net/projects/gptfdisk), launching it on your disk, typing v to get diagnostics on the GPT data structures, and then typing x followed by o to view the MBR data structures. Quit by typing q. Post all that information back here. –  Rod Smith Jan 15 '13 at 17:43

3 Answers 3

It looks like something has trashed your GPT data -- both the main data structures and the backup data structures. I don't know specifically what might have done this, but a buggy partitioning tool seems like the most likely culprit. Another possibility is that there's been some confusion over something like a RAID configuration -- if the disk was originally prepared with your motherboard's RAID features active and then accessed with the RAID features inactive, something like this might have happened.

Two options seem most reasonable at this point:

  1. Re-create your partition "blind." The vast majority of modern partitioning tools begin partitions at sector 2048, so you could use gdisk to create a partition that begins at that point and that ends at the last possible sector. This stands a good chance of succeeding, but there's a risk that if your original partition did not start at sector 2048, you could end up damaging it when you try to access the new partition. Also, some tools will try to create a new filesystem when you create a new partition, so using them would be risky at best. (I recommended gdisk for this task because it does not touch the partitions' contents, just the partition table that defines them.) Also, if the disk held an EFI System Partition in addition to the main data partition, the main data partition would not begin at sector 2048.
  2. Use a tool like TestDisk (included on many Linux emergency systems, such as PartedMagic and System Rescue CD) to search for your missing partition. (There are Windows equivalents to TestDisk, but I don't know what they are, offhand. You could do a Web search to find them, if you prefer to work from Windows rather than boot a Linux emergency disc.) This will be more likely to find your partition if it was placed strangely, but tools like this can become confused if the disk has been re-partitioned in the past -- they can sometimes detect the remnants of deleted partitions and try to re-create them even though they're no longer valid.

Take your pick as to the approach, and good luck! Whatever you do, though, be cautious. You might consider doing a raw disk backup to a spare disk, if you've got one that's big enough to hold all your data. If you do this, though, be very careful in specifying the source and destination disks, or your backup could end up trashing the data you intend to save!

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+1 Thanks for the detailed info. I'll go through this today or tomorrow and see what comes of it. –  Giffyguy Jan 30 '13 at 23:28
    
Option 1 is very risky for the files! –  harrymc Feb 1 '13 at 16:12

Before you do anything - Find/borrow a mac, a USB caddy, and see if you can read it. The only time this has happened to me is when the HDD I used came from a mac and had a GUID boot sector. I didn't completely erase the disc before using. Some very unexplained things happen when the partitions are changed, even though the disc will work fine. An example is whilst installing ubuntu the installer is positive that windows isn't installed already.

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Thanks for the info. However, this drive was purchased directly from Seagate and has been in use by Windows 7 x86 as a non-boot GPT drive in the past. But it seems like this whole "Mac" scenario is a pretty common occurrence, so it's probably good for people to know about it. I'm sure some additional details would be very helpful to some people reading this post, even if it doesn't answer my original question. If you have the time, I'm sure many readers would appreciate some elaboration on the technical scenario you are describing. Thanks! –  Giffyguy Jan 30 '13 at 23:35

I believe that apparently Windows 8 cannot read the GPT structures written by Windows 7, so it shows you the MBR instead, which explains why it shows the disk as 2 TB with 0.7 TB "unallocated".

As a conclusion: You cannot read the disk while booting under Windows 8. Your options are to either find a Linux live CD that supports the GPT of Windows 7, or take the disk to a Windows 7 computer to save your data.

After saving the data, use Windows 7 to erase the disk, do not format it, then try it on Windows 8.

DO NOT operate upon the disk while booting under Windows 8, or you will lose your data !

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I see no reason why Windows 8 would not be able to read GPT structures created by Windows 7. Windows 8 would have to do this when it migrates itself from Windows 7 to Windows 8. As for the author's problem with reading the GPT parition, that can easily be explained, the partition is corrupt. Could have happen in any number of ways, simple solution, put Windows 7 back on another machine and see if it can be read. I am not going to read the comments, way to many, not enough time in the decade. –  Ramhound Feb 1 '13 at 17:03
    
Same solution as mine ... but I must remark again that Windows 8 has many incompatibilities, including its own new NTFS format. And if the disk was slagged, the likely culprit is Windows 8. –  harrymc Feb 1 '13 at 20:31
    
Any documentation that says that Windows 8 will have problems with a Windows 7 NTFS partition because that has not been my experience. –  Ramhound Feb 2 '13 at 0:45
    
@Ramhound: Windows 8 is supposed to be compatible with 7, but several posts in this forum have shown that this isn't always the case. I have seen complaints about network adapters, motherboards, clock and sound that used to work well in Windows 7 but stopped working after the upgrade. So why not also a disk? –  harrymc Feb 2 '13 at 6:30
    
Because there is evidence the the author's file system is simply corrupt. As for driver problems thats ENTIRELY different. –  Ramhound Feb 3 '13 at 18:42

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