I had a similar problem and found that the solution lay in the XP Firewall settings.

It is possible to tell the Firewall that it should permit "His" machine to see "Hers".

I had a Win 98 machine networked to a XP machine and gave each a name and having tweeaked the XP Firewall I eventually.

Initially I had the two machines directly connected through a "cross-over" cable but later set up a hub (or router)connected by standard cables.

Hope you get there in the end.

Dave Earl