How To Hide Drive In Windows Using Cmd Prompt:

You can hide a system hard disk using command prompt. This trick works on following platform:
1. Windows xp,
2. Windows vista,
3. Windows seven.

Steps:
1. Open your command prompt,
2. Just type "Diskpart" and press enter,
3. Now another cmd prompt box will get open,
4. There just type "List Volume" and press enter,
5. It will show the list of disk. Like below.

 6. If you want to hide the drive D then type "Select Volume 3",
     (Then you'll get the message "Volume 3 is the selected volume")
7. Now type "remove letter D",
     (Then you'll get the message "Diskpart removed the drive letter")
     *Then Just open your my computer and see, You'll not find the drive D there.
8. If not just restart your computer. Then check it out.
9. If you want to access the drive again just repeat the steps 1 to 6 and in 7th step instead of remove type "assign letter D". And restart your pc and check your my computer there you can find the drive D now.

Example :

C:\Documents and Settings\support>diskpart
Microsoft DiskPart version 5.1.3565 
Copyright (C) 1999-2003 Microsoft Corporation.
On computer: X-33927C34CD3F4 
DISKPART> list volume
Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  ----
  Volume 0     C                NTFS   Partition     16 GB  Healthy    Syst
  Volume 1     D                NTFS   Partition      9 GB  Healthy 
DISKPART> select volume 1 
Volume 1 is the selected volume. 
DISKPART> remove letter  D 
DiskPart successfully removed the drive letter or mount point. 
DISKPART> assign letter D 
DiskPart successfully assigned the drive letter or mount point.