I'm using a WAMP environment. While trying to work with several sites simultaneously (all of them are originally using the default DRUPAL "files" path and the "public option", I found that the following happened to the file_path of the files that were uploaded before the change was done:

1. From "files" to "newfiles": http://mysite/files/newfiles/... ("files" is not replaced, "newfiles" is added)
2. Changing back to the original configuration OK: http://mysite/files/...

3. From an original "oldfiles" to "files": http://mysite/files/oldfiles/... ("oldfiles" is not replaced, "files" is added)
4. Changing back to the original configuration OK: http://mysite/oldfiles/...

For some reason DRUPAL seems to think that a name different from "files" should be added as a "files" subdirectory! "files" is always there, no way to get rid of it"!

This hampers tremendously the possibility of changing the file system path once a site is installed.
Any light on this will be greatly appreciated.

(This is a copy of my entry in the forum http://drupal.org/node/146522)