DSL doesn't have dial tone, nor does cable. The modem needs a telephone connection to dial out and receive a FAX.
If your modem is still installed, configure XP-FAX, let it find the modem, and plug in a telephone cord. It will use the modem for sending and receiving, and not interfere with the DSL connection as it is connected to your NIC.
How do you get WinFax 10 to work with a high speed DSL modem? Are there certain settings that you have to set?
Do you have to disconnect from the high speed service and then use your regular 56 k modem to use WinFax on your phone line?