Best way to lock down XP User?

I have a friend that wants to allow a remote user to login to her PC and use
only 1 application (an accounting app).

Is there a way to restrict a user to only being able to run a single
application when they log in remotely using XP's Remote Desktop and only
have that restriction for that user's login?

She wants to restrict EVERYTHING ELSE (Windows explorer, all applications,
CTRL-ALT-DEL, etc.) except for the one application.

I know there is kiosk software that will lock the whole PC.....but what
about the same kiosk idea.....but on an XP user basis and not block
everybody out?

Any ideas?