Locking Down Specific Drives

A couple of things come to mind.

If you want the partition to be completely hidden simply use Disk Administrator to delete the drive letter--rendering the drive inaccessible.

If only a subset of users need to be denied access then permissions must be setup so they cannot access the drive(s). This, of course, does not hide the drive from the users that do not have access.

This, of course, will render the drives redundant or redundant while that user is logged on. My guess is that's not what you actually want.

I think what you're asking is how do you let only the system access these drives, and hide all methods of accessing these drives from the user? There are ways to hide the various methods of browsing the hard drive (like Windows Explorer, My Computer, etc.). If this is in fact what you're looking for, set me a note and I can give you more detail...

If you're using the NoDrives registry key (HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Exploer\NoDrives) then the correct usage for C, D, E is:
NoDrives=28

The basic format of this value is that it use 26-bits of information to turn hide drives. A specific bit being on hides a drive. Drive A starts and bit 0 and drive Z is bit 25. So, drive C is binary 100 (which is 4 decimal), Drive C & D is 1100 (decimal 12) and Drive C, D & E is 11100 (decimal 28). Conversion from binary to decimal can be done with the windows calculator (calc.exe) if you're not familiar with binary/decimal conversion.