Multiple displays problem

[desfry]

I have 2 flat panel monitors which work fine but now when both are connected they appear as a single continuous desktop. When I click Detect displays in Catalyst Control Centre they both have a 1 (one). They used to be 1 and 2. I can't find any way of restoring them to default. Can anyone help? I really need to resolve this as the 2nd monitor is next to useless until I resolve this.

 

[Carthas]

Maybe Eyefinity is enabled? That would make it show up as one display instead of two.