you will either use a folder guard, file encryption or something along the lines of access control, you could also use TWEAKUI just to hide drive D: from anyone who uses the computer.
If your using a newer verison of WIndows, such as W2k, or XP, then you can set up the policy to limit access to certain users.
- Access Denied access control
http://www.nt.unets.ru/john/- Atronic's File Security FREE, Encryption of whole folders (optional also incl. subfolders)
http://www.osborn-software.com/- AxCrypt File Encryption FREE, AES-128 File Encryption, Compression and transparent Decrypt and Open in the original application.
http://axcrypt.sourceforge.net/- ABC CHAOS FREE, Easily encrypt files into your personal data archive
http://www.safechaos.com/abc.htm- KPKFile FREE, security for your sensitive files by encrypting and hiding them.
http://www.geocities.com/john52612000/