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How can I restore the MBR for MS-DOS without having an MS-DOS boot disk or floppy drive. Ideally, I would like to be able to do this from a Windows 7 Win PE disk. The only solutions I've found online say to use fdisk or fixmbr but neither of those seem to come with Win PE.

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    Curious, are you really asking about MS-DOS? Do you actually have MS DOS installed on your computer, or are you just confused? Perhaps you are mistaking MS DOS with Windows command line tools? Apr 25, 2014 at 15:20
  • Using fixmbr is the correct solution in a case like this.
    – Ramhound
    Apr 25, 2014 at 15:28
  • @ChrisInEdmonton, yes. We have two production machines at work that still run MS-DOS. Apr 25, 2014 at 16:18

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fdisk /mbr is not documented but works also in MS-DOS 5.00 (http://support.microsoft.com/kb/69013) Tried today, and yes me too I have some DOS machines in production. Other tools @ http://www.bootdisk.com/bootdisk.htm .

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  • -1 I mentioned fdisk in the post. It is not available in Win PE. I need a solution that works with Win PE. May 9, 2014 at 21:19
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    From windows PE you can try BootSect.exe /help. On My version there is this: /mbr Updates the Master Boot Record without changing the partition table on sector 0 of the disk that contains the partition specified by SYS, ALL, or drive letter. When used with /nt52 option, the master boot record is compatible with operating systems older than Windows Vista . When used with the /nt60 option, the master boot record is compatible with Windows Vista, Windows Server 2008 or later. NOT Tried. Can't assure it Works.
    – MasMarco
    May 12, 2014 at 7:06
  • Another way I'm thinking is, supposing you start win PE from CD, you can always create a CD with boot image from BootDisk.com and use fdisk from there... If you need more info let me know.
    – MasMarco
    May 12, 2014 at 7:19
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Naturally, things can go even more haywire: the first thing you should do is make sure any critical data is backed up. If this is a production machine, then it should be worth making a disk image if needed (of the hard drive). Mucking with boot stuff can easily result in disasters, like looking the partition table, which can be much more difficult to fix.

That's not to say that I'm lacking confidence in my advice. I could follow it without problem. But tools that muck with this part of the disk are often tools that are capable of causing major data loss if they are used improperly. Backups should be done anyway for critical business data, on a regular basis. Well, that's even more important before trying any programs like what I am about to suggest, or other software that I've seen other people suggest in this SuperUser question.

If using Windows PE is causing too much aggravation, you can forget about using tools that come with Windows. There are other options available for you.

If you need to boot DOS, all you need is an MBR that can load DOS.

Boot managers can also do what you seek, and they may be installable from different operating systems (or even different computers). Consider using any operating system to make a disk (CD, or floppy) that uses GAG, and then GAG can boot DOS. Also, GAG can install itself onto the hard drive, so then the machine can directly boot the DOS machine. GAG doesn't come with Windows PE or any other operating system; it doe snot use Windows PE or any other operating system. It's meant to be started from the MBR, and it will take care of what you're describing you want to do.

Or use XFDisk which is available separately but also comes with FreeDOS. That has a boot manager that will fit entirely within the MBR. Ranish Partition Boot Manager may be another option.

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DOS MBR work same as WIN7 MBR. MS MBR have only one task- find Active partiotion and "chainload" it BootSector. You need fix BootSector by DOS, as I know you need SYS command

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  • Welcome to Super User! If the MBRs are really the same (which it is), then why would the OP need to use MS DOS to reset the MBR? Why wouldn't any Windows-based MBR tool work?
    – jpaugh
    Jan 11, 2018 at 19:26

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