Windows – Does the fixmbr command repair the Master Boot Code only or it repairs the Master Partition Table, too

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I know there all kinds of programs out there that advertise fixing the MBR, especially Windows. The Master Boot Record consists of the Master Boot Code and the Master Partition Table, correct? But I never thought about if the windows command, fixmbr, or similar, repairs the whole 512 bytes or it only repairs the Master Boot Code. I think it doesn't touch the Master Partition Table but I'm not quite sure.

In short, does the fixmbr command repair the Master Boot Code only or it repairs the Master Partition Table, too?

Thank you for reading.

I want to clarify the MBR is 512 bytes — 446 bytes for the Master Boot Code, 4 rows * 16 bytes for the Master Partition Table and the boot signature.

source: http://en.wikipedia.org/wiki/Master_boot_record and https://wiki.archlinux.org/index.php/Master_Boot_Record

Best Answer

Only the Master Boot Code is repaired.

Tools like the old dos fdisk with its undocumented parameter called /mbr or windows mbrfix recovery command are able to write the hard disk master boot record without altering its partition table information.

So in short, these tools only write to the 1st physical sector of the disk, that is as you already guessed, its 512 first bytes.

More to read here: wikipedia/Master_boor_record.