Win 98/Win 2k home network.

I have a small, two-computer network in my home. My computer runs Windows 2000 Pro, my wife’s Windows 98 SE. The systems are networked through a 4-port router. I have set shared folders on both computers. There seems to be no problem looking in from the W2K system. From the Win98 system, I can see the W2K system in Network Neighborhood. When I try to access it, whether from the Explorer window or with a UNC command, I get an access restriction which asks for a password. Nothing will get through this. Even the Administrator password.