It is a DOS program to save the loader part of the MBR (Master Boot Record)
sector, and can be used later to restore it later. One usefull use of it
is to restore lilo (linux loader) after installing windows.
Note that it doesn't change
the partition table, so you can't use it to backup the partition table.
It is used in two steps:
1- Save the MBR sector by simply running mbrrestr.com from DOS command
line. It will generate the file mbr.b in the current directory of
size 512B. This file contains an image of the MBR sector. Make this step
before you install windows. And make sure that there
is no file called mbr.b in the current directory.
2- Restore the MBR sector when you need by calling mbrrestr.com again.
The difference this time is that if mbrrestr.com finds the file
mbr.b in the current directory, it will assume that you want to restore
the MBR sector. If this isn't what you want, delete (or rename) the file
mbr.b before running mbrrestr.com. Make this step
after you finished installing windows. And make sure
that the current directory is the directory contains mbr.b file.