I take it you are using a Mac...the best way to do it is to go into your system folder and find Photoshop and then the Prefrences folder. Trash that folder (don't forget to empty the trash)and re-open Photoshop. This will work for any new document you start after, but if you are currently working on something I believe it will keep whatever prefrences that were saved along with it. Hope that helps. I share a Mac at school with several others, my preferences are always messed up. I have learned to do this before I start any new document.