No need to download any thing. Fax service is coming with windows. only thing you have to do is to enable fax service. For that go Control Panel->Add Remove Program->Add Remove Windows Component. Select Fax service chek box then press Next.. Net... finish .(It will ask for windows installation CD )

For faxing Open the document->Print select Fax as printer, then Fax wizard will start.......

Note: For Sending and receiving Fax u need modem in you PC