I ran into trouble trying to install Windows Sharepoint
Services (WSS) when front page was enabled on the default web
site. Even when I supposedly disabled Frontpage on the
default web site, WSS would not install. I got around the
problem by first moving the default web site to another port
(say 8888). Then I'd create a new web site at port 80 and
then install WSS. It installs fine. After that, you can
create web sites at will and they can have either Frontpage
Server Extensions or Sharepoint Extensions but NOT BOTH.