htaccess and wp-admin blocking

I’m trying to stop new users from ever seeing the wp-admin area.
So far I’ve used this hack to redirect away from the wp-admin pages, and then added .htaccess to the wp-admin directory to block users who might simply type a wp-admin page into the address bar.

Whilst this works after a fashion, the wp-register.php and wp-login.php are presumably trying to access the wp-admin directory because going through a new user registration brings up the htaccess username/password dialogue box about 5 times. By clicking ‘cancel’ one can still register but it looks terribly confusing of course.

Any advice? Perhaps the htaccess blocking is barking up the wrong tree..