Modem Can’t Make Data Connection

My grandmother has an HP Pavilion 6630 unfortunately, and I can’t get it to connect to the internet. She called their support line, and you know how it goes… they just give her the runaround. I’ve been messing with it, and I can get the modem tomake phone calls, but it won’t connect to the internet; I’ve used three different ISPs, and the modem dials and tries to establish a connection, but just hangs. I work at Penn State’s computer center, and I’ve tried a lot of different things, but maybe there’s something I’m missing. Anyone got any ideas?