I know that SPS 2003 has many more web parts available than those
listed in the default gallery.

To access and make available i need to select Site Settings > Manage
security and additional settings > Manage Web Part gallery

This should then display a list of additional web parts available to
this particular instance of SPS 2003, however i am given the
following message and no available webparts:

Cannot populate the Web Part Gallery. There are no Web Parts
registered in the <SafeControls> section of the ASP.NET
configuration file (web.config) for this site.

Does anyone know how to resolve this and register web parts in the
<SafeControls>?