You'd be surprised at how often this simple step can solve your problem. Check to see if your phone is plugged into your modem. It you have an external modem, check to make sure it's turned on. Some new computers require new owners to go through a personalization and regionalization process.
Some people mistakenly enter their zip code when asked to enter their area code.
Check to make sure you did this correctly. This feature may be disconnecting you from your Internet access. Then try to make a phone call to your regular phone line and vice versa. This is a great resource for Internet users looking for some assistance. If your problem seems to be more computer related than Internet access related, first use your computer's built-in Help files located under the Start Menu on Windows 98 and under the Help Menu on a Macintosh.