[id10t]

You could run from your desktop, but... it is not likely that your USB modem is a fax modem, and Windows really lacks the simple scripting you'll want/need to loop thru a set of numbers to dial and send a fax to. If they can be sent at night, setting up a bootable CD or dual boot your computer to do it may work, but you could end up needed a true hardware modem in your computer ($50 or so).

To make it work, you'll have a text file with all your phone numbers in it. Call the program, point it to your phone list and to the document you want to send and you are done.