Friends,  in this tetorial I will tell u that how to make ur computer more secure...
Sometimes, ur friends or other relatives harm ur system through the command prompt.
Here is the solution ...

Steps:
1. Go to Start.
2. Click run.
3. Type regedit in Run and hit enter.
4. Now Browse as
Local Computer Policy >> User configuration >> Administrative
Templates >> System
5. Now You will see an item named Prevent access to the command prompt
6. Double click on this item. This will open a pop up window.
7. Select Enabled tab from this window to disable command prompt on your windows based computer.
8. Restart your computer.

Now command prompt will be disabled on your computer.
Now nobody can harm ur PC using cmd. 
Screen shot: