1. Go to Start > Run > Type diskpart
2. A DOS window will appear (see below). Then type list volume.
3. So, if you want to hide drive D, then type select volume 3
4. Now type remove letter D
Diskpart will remove the letter. Sometime it requires reboot.
Now when you want to unhide the drive, just repeat the process. But in 4th step, instead of typing "remove letter D", type "assign letter D".
Open up regedit.exe by using the run box, and then browse down to the following key.
If the Explorer key does not exist, you can right-click on Policies, select New Key and name it Explorer.
The NoDrives key most likely does not exist by default, so you'll need to create it with right-click -> new 32-bit DWORD and name it NoDrives.
This value is a 32 bit number, and the bits are arranged in reverse order with a value of 1 hiding that drive. For example, if we wanted to hide drives A: and D: we would arrange it like this:
Converting 1001 to decimal we end up with a decimal value of 9, so if you double-click on the key in the registry editor, choose Decimal and then enter 9 into the value field.
In order to see these changes, you'll need to restart explorer.exe, which you can do easily from Task Manager or the longer way by just logging off and back on.
To make your drives visible again, simply remove the NoDrives registry key entirely.
This tip will only hide the drive from being displayed, applications and the command prompt will still have access to it, and you can still manually browse to the folder if you type in the path.