Faxing with DSL (Enter Phone Number???)

I am connected to the internet, using a Cable modem, however when I try to setup the fax under winXp I get prompted for a phone number, I don’t have a modem connected via telephone, rather Cable modem, how do I ‘trick’ the fax wizard to allow faxes???

I recently installed WinXp Pro, running on a Pentium 366 512mb ram, 20mb hdd. I realize that that will not be the issue, but just added the info ‘just-in-case’ And that the pentium 366 is the low end allowed on WinXp