For NVIDIA Motherboards

  1. Run - regedit
     
  2. Locate HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\nvata

    If you dont have the nvata key (e.g nforce 3 drivers or older)
    Locate HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\nvatabus
  3. Create a dword value named "DisableRemovable" without the quotes and set the value to 1

NOTE: This will just remove the entry from the Safely Remove LIST. It will not remove the Hard Disk from you System/My Computer. But you can still see your Printers, Scanners, Pen Drives etc.