Download Avast or AVG and spybot search and destroy and set them going. If this doesnt clear it up then report back here for more info.

Also i wouldnt suggest trying to download images of a 16 year old unless you want the feds round your house they monitor IP adresses that connect to these sites that host them in some cases and can do you for attempting to get hold of dodgy material.

Moral of the story is use trusted websites when downloading anyhting