I assume both Joomla and Moodle are on your internal local PC. Using the IP defined by your ISP would not be correct as this is the IP that gets assigned to your router. Your PC should also have an IP defined by your router assuming you have DHCP set up. Usually it is something like 192.168.x.y depending on the brand of your router.
You may wish to enter 0.0.0.0/0 in moodle for allowable IP addresses. Note this is not secure as it allows everybody in but since you are local and behind a firewall it shouldn't matter too much. If you do this what happens?
For me, I run on Windows 7 too, I use Uniserver rather than xampp (shouldn't matter), I define a domain in my local hosts file eg testing.com to be 127.0.0.1 and then I always use testing.com in my urls. I also define www.testing.com to be 127.0.0.1. The only downside of this is that I can never go to the real testing.com website (no big deal for me).
Also try avoid using localhost under windows 7 due to IP V4. Many applications are not really geared up for IP V and when attempting to find localhost get confused and time out. For ex. akeebackup will have problems restoring to localhost under windows 7.
El administrador ha deshabilitado la escritura pública.