pRAnK UR FrNZ..

Open notepad and type this:
lol=msgbox ("Warning a virus has
been detected on your PC. Press YES to
format your hard disk now or press
NO to format your hard disk after
system reboot",20,"Warning")
Then save it as Virus.VBS
and go to the folder that contains it
and open it if a window pops out
saying a virus has been detected it's
working.
Press yes or no to close the
window and put it in the startup folder
of the victim's account.
On startup the window should appear.
Note: This does not harm your
computer as it does not contain virus.
The Yes and no button does not do
anything except closing the window.
And you can edit the virus in the
sentence: Warning a virus has detected
on your PC to any kind of virus
eg.Trojan Horse like this
lol=msgbox
("Warning a Trojan horse has been
detected on your PC. Press YES to
format your hard disk now or press
NO to format format your hard disk
after system reboot",20,"Warning")
Oh in between make sure your victim
does not panic and really reformat his
harddisk. hahaha