I agree with the theory, Keef, but the security of this is entirely illusory.
If somebody can get to your drive c: and can place a little prog into one of the many "startup" locations, all it takes is the next time you reboot the machine and the intruder has total control of the machine. NTFS or no NTFS, etc, makes no difference. Once you can run code of your choice on somebody's machine, all software-implemented security goes out of the window.