Charge of $35.95 on Visa Credit card 3/30/2011 not authorized by customer

I recived my VISA card on it is a charge for $35.95 on March 30, 2011 which I did not authorize and supposedly for Dri*Trend Micro.  I would like an explanation for this charge - I also keep getting a message on my computer all the time that Trend Micro has expired and needs to be renewed - what is going on?  Please please reply soon