This simple and powerful plugin will allow you to quickly find commenter's country (IP, name and flag) directly from within the comment notification email.
Visit the plugin's homepage at
http://www.ip2country.cc for more details.
Simply upload the plugin to the plugins directory or use the WP plugin installer to automatically install it. Just activate it and wait for the first comment notification email to arrive. Note the new link you now have in that email, allowing you to quickly determine commenter's IP and country.