How to fix MBR through command prompt?

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  1. Posts : 3
    Windows 7 RC 7100
       #1

    How to fix MBR through command prompt?


    Question: What commands could I run in the command prompt during the system recovery? I try & run say "fixmbr" but it doesn't work. Say if I want to write a new master boot record how would I do that?
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  2. Posts : 82
    Windows 7 x64 rtm
       #2

    These were commands used for vista, but should still hold true for W7. I've just never needed to use them yet......knock on wood:)

    after selecting repair>cmd prompt, enter:
    BootRec.exe /fixmbr

    you can also substitue the /fixmbr with thes commands:

    /FixBoot. Writes a boot sector onto the system partition to start Windows

    /ScanOs. Scans all disks for Windows installations and displays them to you.

    /RebuildBcd. Scans all disks for Windows installations and prompts you to pick the ones you want to add to the BCD.

    Last edited by Brink; 13 Aug 2014 at 08:58. Reason: updated
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  3. Posts : 39
    Vista Ultimate 64bit
       #3

    billdo - I installed RC1 on my H drive. C drive is Vista. While booted in Windows 7 can I use the /FixBoot command to make the H drive bootable? I think now the systems starts up on the C drive and then gives the choice to start Vista or Windows 7 - Advice appreciated - IM
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  4. Posts : 82
    Windows 7 x64 rtm
       #4

    No don't do that, the commands above should only be used as last resort to repair system.It's best to let your primary active system drive take care of all boot options, which in your case is C: Trying to make drive H active and bootable may have(will) cause severe problems.

    If you wish to boot quicker into Windows7 you can change your default OS and boot menu delay in msconfig.

    Go to Start>Run and type msconfig
    click on the boot option and you will be able to choose default os to start and menu delay.

    You can always set the boot menu delay to 0 to boot directly into your default OS and then use F8 or F5(varies different motherbaords)during post to select OS to boot.

    If you want the boot menu to show with shorter delay(default 30sec)be sure to add a couple of extra secs to delay.If you choose a delay of 5sec you may only get 3-4sec.
    Last edited by billdo; 21 Jul 2009 at 14:28.
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  5. Posts : 39
    Vista Ultimate 64bit
       #5

    billdo - After changing the boot drive to H from C, can I remove my C drive, and change H to C? Hey, I really appreciate your help - IM
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  6. Posts : 82
    Windows 7 x64 rtm
       #6

    I wouldn't advise it. You are going to have a lot of confused programs not knowing why their data is no longer on H
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  7. Posts : 8,476
    Windows® 8 Pro (64-bit)
       #7

    Or you could've just tried bootrec /fixboot and bootrec /fixmbr.
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  8. Posts : 3
    Windows 7 RC 7100
    Thread Starter
       #8

    dinesh said:
    Or you could've just tried bootrec /fixboot and bootrec /fixmbr.
    Okay tried all that. The bootrec /ScanOS sees the OS but with I enter bootrec /RebuildBCD it (Y)yes it says "Element not found."

    What now?
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  9. Posts : 8,476
    Windows® 8 Pro (64-bit)
       #9

    justinstrack said:
    Okay tried all that. The bootrec /ScanOS sees the OS but with I enter bootrec /RebuildBCD it (Y)yes it says "Element not found."

    What now?
    try bootrec /fixboot
    fingers crossed.
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  10. Posts : 1,403
    Win 7 Ultimate 32bit
       #10

    Just a little warning to those who may not know....

    Playing with the MBR is a risky thing.
    If you don't know how to recover data and haven't done/or don't know how to do a backup.
    Then you shouldn't be messing with the MBR at all.

    Simply running /fixmbr can and has corrupted it for me several times in the past.
    This is not something that a simple windows repair can usually fix, usually.
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