I am following a photoshop tutorial for designing web page. And after I used the slice tool, I could not delete the following 01 slice. The View->Clear Slices is grey and right clicking the slice shows grey delete slice option. After promoting this auto-slice into user-slice, the delete slice option is accessible but after deleteing the promoted user-slice, I get back the auto-slice.

How could I manage to delete this slice?(I am using Photoshop CS5).
Thanks.