To delete some files I made in AR I had to:

Start : settings : control panel : folder options : view
and click on :show hidden files and folders

then

C: / documents and settings / (user name folder) / Application Data / Ambient design / Artrage (2?) / resources / stencils
then delete the desired file(s).

or place it in a different file.

Another place where stencils are stored is
C: / programs / Ambient design / Artrage (2?) / resources / stencils.