Problem connecting to Perlico broadband

There is some setting on my sisters computer that must be wrong to access the Internet. A friend of hers could connect no problem with his laptop but still no joy with the other computer. Firstly, what connect will it be under? There is a "broadband" and "lan or high speed Internet" connections available, which would be the Perlico option? When we try and connect using the "broadband" one it shows "connecting through WAN mini port PPP03" message and then "Error 678". If we try the other connection it tries to connect indefinitely but no joy. We're lost with very little knowledge, and help would be great...