Ok, I see the problem. What you are doing is:
Are you an IE? If yes, are you IE6? Then you get form_ie.
Oh, you're not an IE? Then you get form_other.
No IE, except 6, will ever get anything included.
If you want only IE6 to get form_ie and every other browser form_other, do it like this:
PHP Code:
if (ereg('MSIE 6',$_SERVER['HTTP_USER_AGENT'])){
include (TEMPLATEPATH . '/form_ie.php');
} else {
include (TEMPLATEPATH . '/form_other.php');
}