'After Image' of layer content when moving or transforming

This is driving me nuts! I think it may be something to do with how my computer is handling Photoshop, but I cant seem to fix it - nothing on the web (I have fiddled with the preferences, caches etc). When I move something on a layer, its after image remains. If I click the visibility of the background layer on and off it disappears. I cant judge transformations or the positioning of layer content accurately as a result. Please help as it is making Photoshop almost impossible to use!