First check the set-up of the network connection. On XP boxes this is done using:
The precise commands for Win2000, ME or Win98SE vary slighly but are in principle similar.
Under LAN or High-Speed Internet there should be an icon for the connection, e.g. Local Area Connection. Select and Right Click, select Properties. On the General tab, part way down is the list of items the connection uses. This should include at least:
Select Internet Protocol (TCP/IP), Select Properties. If the router is set up as the DHCP server then it is simplest to ensure that the adaptor/connection on each PC is set to "Obtain IP address automatically". Thus the PC picks up its IP address from the router. The alternative is to manually enter IP details on the PC. The "Obtain IP address automatically" is usually the best option to select.
All of the PCs should have a LAN connection along these lines. In the case of wireless connections then the wireless LAN connection are the same in principle as for wired LAN connections.
Check the PCs, ensuring that they each:
To help troubleshoot:
If it is still not working then under the LAN Advanced TCP/IP properties that in the WINS tab check that the "Enable NETbios over TCP/IP" option is ticked. On 98SE PCs I have never had to do anything with this (it is ticked by default) but at least check.
Every now and again someone suggest it is necessary to use the NETBEUI protocol in setting up a (Windows) LAN. In this case, with XP Home, NETBEUI is an unncessary addition. Reasoning: it is not in the standard XP installation, it is likely in the long-term to die, if a hardware firewall router is in place, and if a software firewall is also in place (and there is a very strong argument to be having both in any circumstances anyway) then the installation of another protocol is simply additional work that is unnecessary and confusing.
When troubleshooting turn off any firewall software you may have. After everything is working as expected/required then the firewall can always be switched back on again.
The Windows World of Networking site which addresses networking for all Windows variants. The XP and 98SE link deals specifically with Networking between WindowsXP and Windows95/98/ME.