I have configured Windows Server 2008 fax and can send faxes from the server and Vista clients. I am unable to send faxes from XP clients. I can connect to the shared fax printer from the XP clients, however when I try to print to it, it appears to be working, but I never get the window asking for the fax number.
I've added the 32 bit drivers, as suggested at http://help.wugnet.com/windows/32-bit-fax-print-driver-W2008-x64-Fax-Serverftopic-613269-days0-orderasc-8.html
and in another article here on EE, but it still isn't working.