Network issue with Windows XP…

I am currently trying to network 2 XP Home edition systems and have encountered a bit of a snag. The downstairs machine can ‘see’ the upstairs computer, but cannot access any files, Cannot find server \\Upstairs… The upstairs machine cannot see the downstairs one at all. They can both ping each other, and for simplicity sake I have shared out both harddrives at the root. I have changed the network card in the upstairs one and run the net diagnostics on it. In net dianostics the NIC always fails but it can connect to the internet. I have setup the network from scratch using the good old workgroup “Test” but to no avail. The upstairs machine takes a very lone time to go from Client for Microsoft Networks to the workgroup Test and longer still to Open the workgroup without even seeing itself in there. Any suggestions?