If you want to hide some drive letters from the windows explorer then you can use registry to achieve this.
Open registry editor (regedit.exe) and navigate to the following location:
If the key Explorer is not present under the Policies key, you can simply create a new key and give the name Explorer.
Under the Explorer key, create a new 32-bit DWORD and name it NoDrives.
The important thing is the value to be given to that parameter. Below is a table showing the list drive letters in reverse order. To hide a drive letter, you must put 1 for that letter (or 0 to unhide/show). The resulting binary number is the value for NoDrives parameter.
If you want to hide drive letters A,B,D,E and F for example (as shown above) binary value will be : 111011 (remaining zeros not used since no drive letter left to hide, you must go until covering all drive letters considered to be hide).
You need to convert 110111 binary to decimal (http://www.binaryhexconverter.com/binary-to-decimal-converter may be used) which is equal to 55.
Then modify the previously created NoDrives parameter to 59.
Be careful to select Decimal as Base.
Table shown in the below has values for some common drive letters. You may sum decimal values for which drive letters you want to hide.
For the example given above, if we sum 1+2+8+16+32 we reach 59 for hiding: A,B,D,E and F.
Restart the computer. Thats all done!