Whats the exact error you get?
To check if the modem is functioning go to Control Panel - System - Hardware - Device Manager - Expand Modems - Double Click the modem(should only be one listed) - here you can see the modem settings, status, and do a Diagnostics (Query Modem). If the modem driver needs to be reinstalled you can do that by downloading the latest driver from Compaq's website and installing it. AOL should also be able to help you over the phone setting up their browser/software/connection.