Help with troubleshooting a dialup link to the Internet with Windows XP?

My brother has been using dialup access to the Net. He clicked on an option to work offline while on a website, and now cannot log into anything online. Message appears saying that the home page cannot be reached because he is offline. I use Linux; no experience with Win XP, but I'm trying to determine what could be changed in his setup short of doing a System Restore. I'm probably overlooking something simple. Suggestions welcome. Thanks!