Windows XP for untrusted users

Archived from groups: microsoft.public.windowsxp.security_admin (More info?)

We have a number PC's connected to our network that are available for the
general publics use. They only need access to one application. These
computers and the user logons they use are currently members of Active
Directory. I have used group policy to lockdown these PC's to the best of my
ability. This is relatively sufficient however I would like to remove access
to the start menu and taskbar. I am hoping their is a way to configure these
PC's to act in the same manner as a kiosk does.

So far as I said I've used group policy, looked into using an alternative
shell such as blackbox for windows and finally using no shell and configuring
the application they need to run at logon. The latter seemed the best option
in conjuction with group policy to disable access to task manager however it
appears this application requires a shell to run.

I know their are 3rd party commercial products but it seems to me this
should be possible without throwing money at it. Anyone have
experience,suggestions,links etc. to help me out?

Thanks in advance.