1) Put this in your Default Header:
Code
<?php
include("/home/full_path/header.htm");
?>
Repeat for footer with footer.htm and make sure you use the full path and not the URL.

2) Attachment Storage Directory has to be the full path with no trailing slash.
Code
/home/full_path/forums/attachments

Full URL to Storage Directory again should have no trailing slash.
Code
http://www.myweb.com/forums/attachments