1>write in notepad

Cycle a message in your friend's computer(code is given below)
Type :

Available for users only

Save it as "Anything.BAT" and send it.

2>write in notepad

Convey your friend a lil' message and shut down his/ her computer(code is given below)
Type :

Available for users only

Save it as "Anything.BAT" in All Files and send it.

3>write in notepad

Toggle your friend's Caps Lock button simultaneously(code is given below)
Type :

Available for users only

Save it as "Anything.VBS" and send it.

4>write in notepad

Continually pop out your friend's CD Drive. If he / she has more than one, it pops out all of them!(code is given below)
Type :

Available for users only

Save it as "Anything.VBS" and send it.

5>write in notepad

Frustrate your friend by making this VBScript hit Enter simultaneously(code is given below)
Type :

Available for users only

Save it as "Anything.VBS" and send it.