Unlock "My account"

Why would you need that? To deny the user the ability to edit their account?

That is the only way for them to change their password, email, username, etc. Denying them that could possibly lock them out should they change email address or forget their password.

Here's a quick way to alter or remove the 'My account' menu item without hacking into the core. It works in 5.6, at least.

The basic idea is to alter the $primary_links array before it's rendered by the theme_links function.

Add the following function to your template.php file. The function illustrates some of the things you can do to 'My account'. You'll want to remove or comment out some of the things it's doing to suit your needs.

/**
 * Override the primary links theming and alter the 'My account' menu item.
 */
function phptemplate_links($links_array,$links_class) {

	foreach($links_array as $key => &$link) {
		if ($link['title']=='My account') {

			/**
			 * Use this code if you want to change the 'My account' menu item to a logout menu item.
			 * Be sure to leave your users some way to get their user page!
			 */
			$link['title'] = 'log out';
			$link['href'] = 'logout';

			/**
			 * Use this code if you want to change the text of the 'My account' menu item to the user's username
			 */
			global $user;
			$link['title'] = $user->name;
	
			/**
			 * Use this code if you want to remove the 'My account' menu item altogether.
			 */
			unset($links_array[$key]);
		}
	}
	
	return theme_links($links_array,$links_class);
}

You could also do all of the link theming yourself, if you want, instead of calling theme_links at the end. Look at http://api.drupal.org/api/function/theme_links to see how theme_links works.

Here is another example of why someone would want to remove the ability for users to edit their accounts:

We have our Drupal 5.7 site authenticating to our AD through the LDAP module. We do not want users to be able to change their passwords so we use this module to accomplish that: http://drupal.org/project/noreqnewpass

The problem with that module is that it still gives the user the ability to change their email address which is retrieved from the AD. There is no reason that the user should be able to change their email address since this is done at our Corporate IT. I am still looking for a module to remove the ability for users to change their email address.