it might be also useful to know the WordPress version you have installed. This is NOT an XAMPP issue, but I will try to direct you in the right path.
My 'first reaction/guess' is that you have not made a valid entry (one that works beyond the local machine) in the WP Setup for Site or WordPress URL
Look in Dashboard > Settings > General at these values
WordPress address (URL)
Site address (URL)
If they are 'localhost', things will not work right except on the machine it is installed on. IF you do not have a either a registered domain to point your External IP to OR 'hosts' files entries to allow DNS resolution ... then the URL must be set to the local internal IP address of the host machine.