First you need to find out what protocol your network is using. It is most likely TCP/IP or NetBEUI.
If you find these directions too confusing, use the Network Setup Wizard in Windows XP at Start> All Programs> Acceseries> Communications.
If it is TCP/IP change all the IP addresses. The first computer should be 192.168.1.1, the second 192.168.1.2, the third 192.168.1.3, the forth 192.168.1.4, the fifth 192.168.1.5
Each computer MUST have a different IP address, but the subnet must be the same. Change the subnet to 255.255.255.0
Uninstall any other protocols that are not in use. On the XP PC: Go to start > connect to> Show All Connections. Right-click on Local Area Connection and click on properties. Set all the TCP/IP settings for your network adapter.
If you are using NETBEUI, you must install this protocol from the Windows XP CD. It is available in the folder D:\VALUEADD\MSFT\NET\NETBEUI (where D is your CD-ROM drive)
Follow the directions in the text file.