HIDE YOUR DRIVES(C:,D:,E:)

This is a great trick you can play on your friends. To disable the display of local or networked drives when you click My Computer.

1.Go to start->run Type regedit Now go to:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Now in the right pane
create a new DWORD item and name it NoDrives (it is case sensitive).
Now modify it's value and set it to 3FFFFFF (Hexadecimal) .
Now restart your computer.
Now when you click on My Computer, no drives will be shown
To enable the display of drives in My Computer, simply delete this DWORD item that you created.Then restart your computer.You can now see all the drives again.

You can scare the hell out of ur friend if its done in his computer without letting him notice.