Reset theme settings problem

Hi,
I’ve recently modified my style sheet and a few others I can’t remember. All in all I’ve completely messed it up. I’ve deleted my theme, downloaded a fresh copy and reinstalled it.

The problem is that it keeps the same settings and I can’t get rid of it. Like it displays a specific colour theme which I’ve chosen previously rather than the default and the same banner link I’ve uploaded is still there.

Does anyone know how to make wordpress think that it’s a completely new theme and it’s never seen it before? I would like a fresh start on my freshly installed theme.

Thanks for helping!
-Ashley