theres like 6 or 7 types of klez, i think you should find out which one it is and do some looking up on it and see what it attacks and how. i had klez.i for a while,thats what got me looking into Av's more as most that i tried could'nt remove it.

IMPORTANT:

BE VERY SURE THAT IT IS GONE BECAUSE A TRADE MARK OF klez IS TO COPY ITS SELF AND HIDE.
MANY OF MY av'S THAT I TRIED OUT SAID THE CLEANED IT BUT IT KEEP REAPPEARING.
hope this helped.