Huh?

"Can you stop [the] Contacts and Calendar folder [from] appearing ..."

Okay, understood you so far.

"... in every other folder ..."

Still understood under the presumption you are talking about folders
other than Contacts and Calendar within the same message store.

"... you appear to attach files from?"

Appear?  Are you saying attachments are showing up in the new-mail
editor window when composing a new e-mail but which you did not
explicitly choose to attach?  Folders don't get created when you are
attaching items from them into an e-mail.  My guess is that somehow as
yet to be described that you are attaching items from a folder to a new
e-mail that you are composing.  Whether you are dragging the item into
the new-mail editor window or using the Insert menu, new folders don't
get created.

You need to better explain just exactly what you were trying to do.