Hello Guyz, today we are going to teach you a very simple but very dangerous trick which you can try out in your friends system :P >_What are we going to do : We will change some of the important file formats like( exe, cpl, bat, msc, mp3 , mp4 , flv or any other of ur choice) into txt format. >_ What will happen : Whenever ur friend will open any file with the above mentioned extensions for example suppose if they open any video file of format mp4 it will open as notepad and they will never be able to play that. So lets get started : Step 1 : We need to access ur victims/friends machine at least for 10 minutes. Step 2 : Type regedit.exe (registry) in run prompt of the victims machine. Step 3 : Now you are on the Registry window -> Click on " HKEY_CLASSES_ROOT " and search for the extension you want to change. Here we are changing any executable file (.exe) to text file(.txt). Similarly you can also change of you own. Step 4 :