We need to activate Design Mode where all objects are selectable:
Tools > Customize > Toolbars : Tick "Exit Design Mode"
(Although Excel 2003 calls the button "Exit Design Mode" it is in fact a toggle switch for Design Mode. I suggest attaching the new small (only one icon!) toolbar to the Excel menus.)
You can now toggle between design mode on and off by clicking the Design Mode icon.
With Design Mode on, select the object you wish to delete (in this case the text box) and delete it...
Switch off Design Mode again. Optionally remove "Exit Design Mode" toolbar from Excel.
