Remove password reset fields on user profile
To hide the password fields on the user edit form, put this code in your custom module, which implements hook_form_FORM_ID_alter():

function YOURMODULE_form_user_profile_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  hide($form['account']['pass']);
}


You may also want to prevent users from going to user/password page and change their passwords on that page:

function YOURMODULE_menu_alter(&amp;$items) {
  $items['user/password']['access callback'] = 'user_access';
  $items['user/password']['access arguments'] = array('administer users');
}


One more hint, if you want to remove the links on the user login block:

function YOURMODULE_form_user_login_block_alter(&amp;$form, &amp;$form_state, $form_id) {
  $form['links'] = '';
}