Within your Zen Cart admin-console, change Configuration->Layout Settings->Define Breadcrumb Status to 2 ("Off" on main page only).

You should also consider (1) upgrading, since Zen Cart v1.3.8a has many security vulnerabilities and (2) making use of the Zen Cart template-override system (continuing to use the classic template for your changes can cause you problems, i.e. files overwritten, when you upgrade your Zen Cart.