Altering authentication

Hi I'm new to drupal development and am need to alter the behaviour of the authentication process so that passwords aren't case-sensitive (ie the input password is strtolower()ed on insert, and there after compared to the db password . I've tried mucking around with hook_user and hook_alter_form, but haven't worked out the best way to tackle it.

If anyone has been down this path before and has any suggestions, much appreciated.

Thanks

Steven