HELP!!! Accidentally Deleted Mac 200Mb EFI Partition in Windows 7

Discussion in 'Windows, Linux & Others on the Mac' started by wayne1116, Sep 9, 2012.

  1. wayne1116, Sep 9, 2012
    Last edited: Sep 9, 2012

    wayne1116 macrumors newbie

    Sep 9, 2012
    Yesterday I installed windows 7 on my iMac and I tried to create a new partition in windows. I saw a 200Mb partition in the hard drive, I thought it was useless so I deleted it and created a new partition X. So I changed the partitions from a. 200Mb EFI partition, b. 800Gb Mac OS partition, c. 200 Gb Bootcamp to 1. 800 Gb Mac OS partition, 2. 100Gb Bootcamp partition, and 3. 100 Gb windows partition X (I created in windows 7). (I cant remember exactly the size of those partitions)

    After I restarted my iMac, nightmare begun.. I pressed OPTION when started iMac, but Mac OS is gone, and only Windows showed up. After I chose Windows, it became blue screen and restarted again.

    I have some very important documents in my 800Gb Mac Partition, so I installed Lion in an external hard drive and started from that, trying to access the 800Gb Mac Partition, but only 2. 100Gb Bootcamp partition, and 3. 100 Gb windows partition X (I created in windows 7) show on the desktop, the 800Gb Mac partition is still not there. I opened Disk Utility, under my 1TB hard drive, there are 3 partitions as I mentioned above. The 2 and 3 are accessible, and I formatted them. But the 1 (800Gb Mac Partition) is in grey, and both verify and repair to the partition failed.

    Later on I tried to use firewire to connect iMac with my Macbook, but only the 2 and 3 partition show up on my Macbook's desktop. 1 is still not there.
    I saw this thread and downloaded iPartition, but after I created a EFI filesystem partition at the beginning of the disk, it was only 1Mb and it didn't work at all. I don't know it was my mistake or this method does not work at all. iPartition.jpg

    It is weird that the size of partitions are different when I check them using different applications. 1.jpg 2.jpg

    Could anyone PLEASE help me with my problem? All my important documents are in that Mac partition. Is there any way I could get them back?

  2. hfg macrumors 68040


    Dec 1, 2006
    Cedar Rapids, IA. USA
    Now is when you pull out your Time Machine backup disk ... you do have one, right? :rolleyes:

    This may help you to see more of what you are working with. The DiskUtility program has an additional menu bar selection "DEBUG" which can be enabled with the following terminal command:

    To enable Disk Utility´s Debug mode:
    kill disk utility if open,
    in terminal: defaults write DUDebugMenuEnabled 1

    Hopefully this will help you, or at least provide more visibility of what your current disk arrangement looks like so perhaps we can help you here. Be very careful what functions you use in the Debug menu ... some can cause more problems!

    Good luck...
  3. Quad5Ny, Sep 9, 2012
    Last edited: Sep 9, 2012

    Quad5Ny macrumors 6502a


    Sep 13, 2009
    New York, USA
    Edit: Nevermind, you did more than just delete the partition, I don't know how you would get them back at this point.

    Edit 2: Try hooking the drive up to a Windows computer with Apple's HFS+ drivers installed.


    If you know the offset and size of the previous partition, you should be able to add it back using GPT while booted into a OS X install disk.

    It would go something like this:

    1. Boot OS X install media
    2. Utilities > Terminal
    3. umount /dev/disk0s1 ; umount /dev/disk0s2 ; umount /dev/disk0s3 ; umount /dev/disk0s4
    4. gpt add -b 40 -i 1 -s 409600 -t efi /dev/disk0
    5. gpt add -b 409640 -i 2 -s 1562500000 -t hfs /dev/disk0
    6. Quit Terminal
    7. Open Disk Utility, Repair disk & Partitions
    8. Copy your data, repartition, reformat & reinstall

    Those numbers will NOT be correct for your drive. They are only correct if you had partitions aligned to 4K and if your OS X partition was EXACTY 800GB (base 10).
  4. Blaine macrumors 6502a


    Dec 3, 2007
    Abilene TX
  5. hfg macrumors 68040


    Dec 1, 2006
    Cedar Rapids, IA. USA
  6. terraphantm macrumors 68040

    Jun 27, 2009
    Notice the large drive is called Windows Dynamic Disk Marker... Depending on if you wrote any data to said dynamic disk, the data could be gone
  7. wayne1116, Sep 9, 2012
    Last edited: Sep 9, 2012

    wayne1116 thread starter macrumors newbie

    Sep 9, 2012
    Hi hfg,

    Thank you very much for your reply. However, I didn't use time machine to backup my latest documents, so that's why I'm so worried. If I have all the documents backup I would just format the whole partition and reinstall the OS...

    Btw, the partition #3 is empty now. It was partition X which I created in windows 7, and I formatted it after the problem occurred.

    Thank you!!
  8. wayne1116 thread starter macrumors newbie

    Sep 9, 2012
    Hello Quad5Ny,

    I really appreciate your response.

    I will buy a hard drive dock and connect the hard drive to my IBM notebook tomorrow. Btw, it is very weird that the size of those partitions are different when I check from different applications (I have uploaded the pictures).
    I have one more questions: Is Apple's HFS+ drivers a software that I could read documents from Mac OS in Windows 7? Or it has more advanced function? I'm asking because I have tried to get access to that 750Gb partition from windows 7 (which I created using bootcamp, but after I got in it once it was not working either), but that part of partition didn't show up in My Computer. I'm wondering whether the same thing would happen again.

    I'm extremely worried about the situation since all my valuable documents (such as graduation pictures and videos) are in it, and thank you so much for your help!


    Not yet.. I will go to Apple Store first to see whether they have any solutions...
  9. Quad5Ny, Sep 10, 2012
    Last edited: Sep 10, 2012

    Quad5Ny macrumors 6502a


    Sep 13, 2009
    New York, USA
    EDIT: "I formatted it after the problem occurred" :eek: Really, you formatted it too? Assuming it was only a quick format your files would still be in place but you probably trashed the file system on the partition. Meaning your probably never going to get back the directory structure/file names (you can still recover the files but they will be unnamed).

    At this point instead of trying to get the partition back, file recovery might be a better option. This program seems promising if the reviews are legit. Maybe other people can offer suggestions for other programs.


    I saw you have a iMac. It's extremely difficult to remove the hard drive from those, don't go out and buy a dock just yet.

    The drivers are the same ones that come with Apple's Boot Camp Windows Support package. They don't do anything advanced.

    Some suggestions:
    • Do not play around with partition utility's.
    • If it was my drive, I would do a 1:1 (using dd) clone and only mess around with the clone. (A cheap 1TB USB would be fine).
    • Don't let the people at the Apple store mess around with it, they are not trained for data recovery.

    You should clone the drive before messing around (I don't want to be responsible for lost data :p). In addition to trying to manually recover, you could try some data recovery software like this (but again only after you have a cloned backup).

    Lastly, you should consider a data recovery service. You can either send them the entire iMac or the cloned drive. Most of the places will do a free evaluation and then give you a price.

  10. throAU, Sep 10, 2012
    Last edited: Sep 10, 2012

    throAU macrumors 603


    Feb 13, 2012
    Perth, Western Australia

    Trying to diagnose this via forum over the internet means you'll get all manner of random suggestions - some maybe good, some not so good.

    Randomly playing with stuff to try and get things back is only going to lessen your chances of successful recovery, because you may be over-writing various parts of the disc that contain info required to reconstruct or gain access to your data.

    Your options are:
    - (preferably) engage a data recovery specialist to attempt to get your data back
    - roll the dice and try to get things back yourself - maybe following advice on here, which may or may not be good advice, and is certainly being made by someone who has not looked at your disk...
    - if option 1 is too expensive and you then fail at option 2 - accept that your data is gone and move on, taking on board the lesson to keep up to date back ups.

    If you had a time machine backup you could simply reinstall via network or DVD and then restore your stuff.

    If you have important stuff, there's no sane reason not to back up - drives die, even without user intervention. If your data to you is worth more than say, $100 (and I suspect, now you face losing it, it probably is) - spend the money on a backup drive next time.

    be very careful with DD. if you get the drive ID's wrong, you could very well end up over-writing your old drive with the contents of your nice new blank backup drive. If you have any doubts as to exactly what you are doing, don't do it - you may very easily be making the situation much worse than it already is.

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