Unless I'm mistaken it sounds like you have a broadband internet connection.
Broadband and Faxing as we know it aren't compatible - differences in the way a telephone fax modem and the broadband modem's work.
There are various companies offering an e-mail to fax service where you can send e-mail via them and the recipient gets a fax...
they all charge for the service though
There are some "Shareware" programs about that may do what you want - take a look at this one :
Phone Fax ISDN
It is free to download and try for 30 days then has to be registered for a one off cost of US $23.00 - doesn't look like there are any ongoing costs after registration.
It may be what you're looking for although I haven't tried it myself.
Coconutty
