http://www.snopes.com/computer/virus/valentine.asp
You may cut and paste that, so you don't fear clicking into a virus download.
I got one about a month ago - the subject line said, "You have a card from a friend". Well, I deleted it, because if it was from a friend, I got a 'red-light' when it didn't use that friend's name.
Be careful - because a lot of people send cards to their friends at Valentie's day - before opening one, you might want to check with your friend first, and make sure they, in fact, did send you a card.
I clicked the link without cutting/pasting. What are the chances that the link is the virus itself?