>I would like to share a modem on a Windows NT network so that I can use winfax software installed on workstations to send fax to a fax number via the shared modem installed on the server

I believe you'll need the Network version of WinFax to do this. If your server is currently running BackOffice, you should be able to enable Microsoft Fax Server on the server box, and install the Microsoft client on the workstations to do what you need. If you want to use WinFax in the network environment, I'd check with Symantec as to what is required for version and station licenses.