Warning! Do not change drive letter of HFS drives.

Discussion in 'Windows, Linux & Others on the Mac' started by skeewiff, Jun 21, 2010.

  1. skeewiff macrumors newbie

    Jun 21, 2010
    Hi all,

    I'm not too sure how widely known this problem is, but I didnt immediately find any specific threads dealing with it - so I guess I'll re-iterate it for the benefit of people like me coming over from PC.

    If you use bootcamp on your mac to run Windows 7 (x64 Home premium in my case), do not use the disk management tools in W7 to change the drive letter of any HFS+ formatted drives. Doing this will trounce the partition table and make them unreadable in mac OSX.

    Even though windows still reports the disk to be HFS, OSX believes it to be MSDOS-FAT and unreadable. Repairing the disk fails with the following error message:

    Invalid BS_jmpBoot in boot block: 000000

    I have tried this a few times now (this time with empty disks!) and can reproduce the error every time.

    Can anyone else who has seen this happen chime in so we can get an idea as to what versions of windows are affected?

  2. spinnerlys Guest


    Sep 7, 2008
    forlod bygningen
    Thanks for the info, but why would you change the letters in the first place?

    I worked in environments (Windows XP and Avid Unity) where one would need to, as there where up to 26 drives connected at many times, but is Windows really not capable of having more than 26 volumes connected to it at the same time?
  3. skeewiff thread starter macrumors newbie

    Jun 21, 2010
    Hi there.

    The audio software (cakewalk Sonar) I use in windows relies on soundbanks being kept in the same location. I.E if a project references the file G:Instruments/trombone , then it needs to find it on the G: drive, and not the H: drive. Windows automatically allocates drive letters, and so to be able to always allocate the correct letters to the correct drives, this sometimes means having to re-allocate a drive letter to HFS partitions to "free up" what is available.

    Hope this answers your question.


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