Today I want to show you that how to block/lock your local hard drive.
Step 1:

go to Start>>Run and write "gpedit.msc" then press OK. A Group Policy window will be open, Image below -
Step 2:

After openning the Group Policy click on the left side of the Policy window.
User Configuration>>Administrative Templates>>Windows Components >> Windows Explorer> in this Page you can see a lots of processes. Findout the "Prevent access to drives from my Computer" and double click on it. A pop up window will be open. Now choose Enable options and Pick one of the following Combination from this window. Finally click on Apply. thats it.
Now open your "My Computer" and try to open your any Hard drive. Yes its Locked.....
Repeat this action for Remove the Block/Lock.