Your existing Microsoft fax application will not work after upgrading to Windows XP. Uninstall this fax application using Add/Remove Programs in Control Panel, and then restart the upgrade. 

After installing Windows XP, add a fax printer connection to reconnect to the Fax Server, and use Windows XP Fax to send and receive faxes using this connection. 

For a list of software supported by this version of Windows, see the Microsoft Windows XP Product Compatibility List at http://www.microsoft.com/windows/compatible.