RawDisk

RawDisk allows you to implement an application accessing Windows 7, Windows Vista or XP disk directly.

The sectors can be read or written from user-mode processes, thus going around direct access ban imposed by the OS.
RawDisk allows access to files that are already opened or have restricted access security setting. This significantly simplifies implementation of backup applications.
Ability to write and read disks sector by sector without operating-system-imposed restrictions comes in handy for development of data recovery, undelete and forensic applications.