Speed up data flow

My company recently switched to Windows Server 2003 running workgroups w/XP
Pro PC’s. We have a “Business Intelligence� Excel spreadsheet created by the
software co. on the server and a mapped shortcut on a few PC’s. It takes a
(long) while to refresh the data and nothing else can run at that time. How
do you speed up the data flow between the Server and the PC’s? One of their
software tech’s said there might be a way. Any help would be greatly
appreciated.