I don't use winFax, I use V3-CallCenter, but I guess
it's the same.
You need a phone-modem, but you don't need a ISP.
You don't need a fax machine at all. The modem works
as a fax machine.
A scanner does come in handy.
If you already have a fax machine, I'm not sure how
you would/could tie that into a computer.