well, there is a Registry tweak that will hide any drive.
Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Name: NoDrives
Type: REG_DWORD
Value: To calculate the value, add together the numbers for the drives you want to hide, using the formula: A=1, B=2, C=4, D=8, E=16, F=32, G=64, and so forth. To hide D: & E:, the value would be 8+16=24.
So, you could set it that way. Now, another easier way to hide a drive is to download and install TweakUI from Microsoft. One of its sections (under the MyComputer tab) lets you click a checkbox beside any drive letter you want to hide. Uncheck the D: drive, click OK, and that is it. Easy.
You can download TweakUI here:
http://www.microsoft.com/ntworkstation/downloads/PowerToys/Networking/NTTweakUI.asp