slow network

I have 5 systems on a microsoft network. My main system and 2 others is windows 98se with D-link 100 card. I am using a belkin router, sharing a DSL modem. 2 system has windows xp pro. It takes over 40 minutes to transfer a 4.5 gig file. This seems slow when you can download a 4.5 file in less then 5 minutes. I am using tcp protocol. All cards are working at 100 mbps. I have removed the router and used only a intellinet network hub.
Any suggestions?