Thanks rgd, I updated the post above stating why I did the plugin originally. And well, I hope some new developers might learn a bit from the code to understand q2a better :)
I think I gonna merge the plugin, as mentioned above, with the new users page and build a widget, so it is more comprehensive. Stay tuned.
For others that just search the admin option, go to: admin/spam and enable "Email me when a new user registers:"