|No need to apologise, you've given enough information for others to help.|
Sounds like a "Master Browser" issue - common in mixed OS networks. Sounds technical, but in simple terms, you have W98 in control (your "Host"), and one of the other PCs "takes control" of the network. Whether that happens or not depends mainly on the order each PC connects to the network (and which side of the bed you got out of in the morning -I'm serious!).
XP (or Windows 2000) has a habit of taking control, confusing the other PCs, and has to be stopped from doing so.
In XP: Start menu -> Programs -> Administrative Tools -> Services
Double-click on "Computer Browser" and change "Startup Type" to "Disabled" and then click "Stop" and then OK.
Another route to Services is right-click on "My Computer" and select Manage, but this shows you a load of other stuff you're not (or shouldn't be) interested in.
If you have a problem, post back with details. If not, post back anyway, it's good to know when a problem is solved, and it might help others too.