How to completely delete a theme and its settings?

Hey!

I am new to using wordpress and have been coming across a problem.

I recently download a few themes and I also FTP a theme into the folder. I am trying to uninstall a theme and all its settings that I’ve done. So I went to appearance, themes, uninstall, done! Now I wanted to re-install that theme again (Because of lost/deleted information from experimenting) but when I FTP the theme back into the proper folder, went to wordpress and activated. For some reason is kept all my information from last time. I didn’t want that! I wanted to start from scratch again.

So how can I do this. Delete the theme and when reinstalling, its all blank. No information is kept. For instance the change I did to the widgets, etc.

Hope this make sense.

Thanks