Virus problem from MSN

Recently
A BIG BIG trouble show up
is about MSN and virus

here is what happened
that day
as usual sign in msn messenger
and saw one of my friend send a file to me
because she sometime will send some pic file to me
so i just accept
after finish sending only I realise is a virus
why I say so?

Because
It immediately and automatically send to my friend list
and after that
all the window that show that I send the file will be invisible
so I got no chance to stop
the only thing I can do is just sign out my msn messenger

BUT
story haven't end
before you success sign out
you got to off a lot of window that ask you whether sure to sign out,because once you sign out,all the window will be off
how many friends of you online
how many window you need to off
damn troublesome

NOt Only that
the file sending will not only occur once
It will try over and over again
try to send to your friend list

OH MY GOD!!!!!!!
can someone save me from that????
I getting crazy because of that

OR I should reformal my laptop???

Anyone got any suggestion???
I hate it!!!!!