hide the hard disk drive

open command prompt
and type DISKPART at command prompt

DISKPART> list volume

Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 E CD-ROM 0 B
Volume 1 C NTFS Partition 20 GB Healthy System
Volume 2 D Local Disk NTFS Partition 55 GB Healthy
Volume 3 F HARI FAT32 Removeable 1956 MB

after that type list Volume
and select volume 2 (in case of volume 2)
and type
remove letter D (here D is the correspond letter for Volume 2)
it will show u message
DiskPart successfully removed the drive letter or mount point.
and go to mycomputer and check for the drive
to show the drive
type
assign letter D
and check my computer