Problem with Dell SP2009W 20" display on Mini

I am using a Dell SP2009W 20" display with my Mac Mini. The highest resolution is 1680x1050. However, when I try to change the resolution to this, it leaves a large column of black space on the left of the screen and I can't figure out how to resolve this so the 1680x1050 res works with the entire screen.

Gone into the display settings and nothing makes a difference there.

it is currently on 1600x1000 which is a bit blurry, albeit fills the entire screen.

is this a problem anyone else if familiar with?

Any ideas, tips, advice is greatly appreciated.

Thanks,
Ally.