NT_Worker

There is a physical device that creates a separate partition and records all hard disk changes there, so the machine will revert back to it's original state upon reboot. This will undo *any* change to the hard drive and software. I was told (by witnesses) there is a way to do this with NT 4.0 workstation with out the need for the physical device. I would like to know how to accomplish this. In any OS at this point. Thanks...