function of @ key.

When I press the @ key on my keyboard it types " instead of @. The reverse of this is when I press the " key I get the @. I think this is due to American settings for the key board and a colleague changed this for me on another laptop of mine but I can't remember what he did.

Does anyone know how to resolve this so that these two keys truly represent and produce what is shown on the key for them?

Regards

John