To Install the built in Windows XP fax software component use the "Start" menu, then select "Control Panel", then "Add or Remove Programs", then "Add/Remove Windows Components" to get to this screen:

Check the "Fax Services" box and then click "Next" to run the Wizard. When finished you should see the following screen under "Printers and Faxes" under the "Start" menu. You'll find the "Fax Console" under the "Start" menu listed under "Accessories" under "Communications". Or you can simply select "Fax" as your printer when you use the print menu. Read the Microsoft help files at the links listed below for more help.

Enable and configure the Fax
service: support.microsoft.com/kb/306550/
Send a fax in Windows XP:
support.microsoft.com/kb/306657/
Fax a document from a Windows program: support.microsoft.com/kb/306661/
Receive a fax in Windows XP:
support.microsoft.com/kb/306662/
Fax a scanned document in Windows XP:
support.microsoft.com/kb/306663/