[jeremye]

I'm not sure what version you're using, but look in include/register.php. In my version I have a send mail function such as:

#
# Send mail to registered user
#
func_send_mail($newuser_info["email"], "mail/profile_modified_subj.tpl", "mail/profile_modified.tpl", $config["Company"]["users_department"], false);

In order to use either TEXT or HTML, I would suggest something like this:

#
# Send mail to registered user
#
if ($userinfo[htmltext] == "Y")
	func_send_mail($newuser_info["email"], "mail/profile_modified_subj.tpl", "mail/profileHTML.tpl", $config["Company"]["users_department"], false);
else
	func_send_mail($newuser_info["email"], "mail/profile_modified_subj.tpl", "mail/profileTEXT.tpl", $config["Company"]["users_department"], false);

Again, I am not sure of version info, or if the variables used above will work in your version, but this should get you started...

Let me know if you have trouble implementing it.