This tweak will hide a drive letter from showing up in My Computer, however the drive will still be able to be accessed manually by typing in the drive letter in explorer.
----Tweak Steps----
1) Start > Run > regedit
2) Goto HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\
Explorer
3) Right click in the blank space and choose New > "REG_DWORD (DWORD Value)"
4) Name is "NoDrives"
5) Right click on "NoDrives" and select Modify
5) Following the table below, enter in a DECIMAL value!!
To Hide Multiple Drives, Add their values together.
Example: A+D = 9 Decimal Value
A+C+D = 13 Decimal Value
6) Press OK
7) Close regedit window
8) Note: A restart may be required, however I did not require one.
Hope This Helps!
-James Hartig