Hi Heatherly,
To disable the store window, please go to Auctiva -> My Account(tab) -> Settings(Preferences), uncheck the box next to "Enable Store Window" and save. This will prevent the store window from being added to any of your newly posted listings.
To remove the store window from your active listings you must delete the store window html from the html description using eBay's "Revise Item" form. The html description can be found at Auctiva -> Store -> Store Window -> Store Window HTML. The store window html lies between ASW tags.
-Mike