[Zope-CMF] question: changing the portal_type

[Roel Van den Bergh]

We have a site filled with files to download.
Because zope does not make any difference between filetypes like *.doc,
*.pdf or *.dwg we tried to ad our own filetypes to show the appropriate
icons.
But even when I change the content_type by hand the icon does not change.

I would like to write a script that changes the content of a folder to a
specific portal_type but I do not know where to start.

Can somebody please help us?

TIA, Roel.