How to make a modem answer a fax call?

I have a Dell PC that has a data/fax modem inside it. Attached to the computer is a USB printer/scanner.

We are meant to be able to use the printer to send and receive faxes, and have been able to do so in the past. Recently, we have had to completely re-install the system. I have used the original Dell disk and have been careful to ensure all the necessary applications have been installed.

We can connect to the web, and send and receive email.

When we receive a fax call, the computer used to answer it, and send the information to the printer so that is was printed out.

Now, when we receive a call, the computer does not answer it, it just lets it ring and ring.

Any ideas on what I need to do to get it back to how it was?