This depends on how the registration page is coded.
For instance, when i make a php login form it is never case sensitive, because i always call the strtolower function.
ALSO, the password should NEVER be stored in a database, only the encripted version, here is what i use both on the registration page, and the login page
PHP Code:
$password = htmlspecialchars(addslashes($_REQUEST[password]));
$hash = "_24+(c";
$pass = md5(md5(strtolower($password)+$hash)+$hash);
$password is the input from the login/registration form
$hash is a random hash code
$pass is the encripted password is encrypted it is already in all lower case no matter what the user inputs into the form.
Does this help at all?