Getting better all the time,
It couldn't get much worse.
Spent all weekend trying to fix the network. I was sure it had something to do with windows XP or TCP/IP. Surfing for a solution late Sunday night I came across a suggestion to try the IPX/SPX protocol. Came into the office early this morning full of optomism, only to be badly disappointed. Still no joy.
The network is laid out over three floors with a hub for each floor, daisy-chained together. After some "advanced fiddling", I got the two PCs on the top floor to connect to each other, though they couldn't see the rest of the network. I then took a laptop and started plugging into the different hubs to check connections.
Turns out the middle hub was faulty. By coincidence all the XP machine were connecting to the server through the faulty hub, while the 98 machines just happened to be on the same hub as the server.
If only I had figured this out three days ago. 😥