The "localhost" IP is 127.0.0.1 (not your Internet IP address).
My installation of WAMP has the following line at the end of the httpd.conf file:
Include "c:/wamp/apache2/conf/alias/phpmyadmin.conf"
That file consists of:
Alias /phpmyadmin/ "c:/wamp/phpmyadmin/"
# to give access to phpmyadmin from outside
# replace the lines
#
# Order Deny,Allow
# Deny from all
# Allow from 127.0.0.1
#
# by
#
# Order Allow,Deny
# Allow from all
#
<Directory "c:/wamp/phpmyadmin/">
Options Indexes FollowSymLinks MultiViews
AllowOverride all
Order Deny,Allow
Deny from all
Allow from 127.0.0.1
</Directory>
I am then able to access phpMyAdmin with the following URL:
http://localhost/phpmyadmin/