If you really, really, really, don’t want the GP Homepage you can of course click customize this page and turn everything off. If that’s not good enough for you, Mohammad Daoud has a new post up with another option that replaces the GP XSL Homepage code with logo you choose.
Replacing the GP Homepage With a Logo
Archived post from 2009. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.