Take the Magic Jack out of the network while trying to solve the laptop connection issue. That alone may solve your connection issue.
Take a look through your router user manual for turning the connection on to the laptop, if you don't have one -- use
THIS one, which is very similar.
You may also want to check to see if the XP laptop is getting a dynamic address by going into the network control panel, click properties, highlight Client for Microsoft Networks and click the Properties button on that page. It should have your settings listed there.