hide your hard disk

Click Start -> Run type regedit in the box and click OK
Navigate to:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\
Explorer

From the menu, navigate to Edit -> New -> DWORD Value
Name the New Value NoDrives
Next, Right click NoDrives and select Modify, now check the Decimal option and under Value Data enter a decimal value for the drive you would like to hide. For example to hide C you would enter 4. See the list below for more values:
A=1
B=2
C=4
D=8
E=16
F=32
G=64
H=128
I=256
Click OK once finished and restart your PC to verify the drive letter is no longer displayed

Note: You can delete the key that was created to display the drive again.