HDHacker is a freeware micro-util that saves, visualizes, restores the MBR (from a phyisical drive), the BootSector (from a logical drive) or any sector from a disk too.

It can be used, for example, to save and restore a particular boot manager (as LILO, for example) in case of a Windows new setup (that, obviously, overwrites it).

An MBR and BootSector backup can also be useful for simple precautionary purposes too, in fact sometimes viruses or other SO (Linux) setup could overwrite them and/or alter them, so it is impossible to start up previous SO and/or have access to datas stored on the disk.