In theory, uninstalling the network cards and any software that came with the network cards ought to remove all traces of networking. However, no-one here could guarantee that. The only way that you'll absolutely definitely clear it all out is to format the PCs and install Windows from scratch.

You shouldn't need to wipe everything off though. The networking is already working at a basic level as they are connecting to the Internet through the router. That means that they are all using correct IP addresses, which is the fundamental thing that needs to be right. The second thing is to put them in the same workgroup. This is easily done. In Windows 2000 / XP, right-click on My Computer, go to Properties, go to the Network Identification or Computer Name tab, choose the option to rename the PC or change the workgroup/domain and then enter the name of the workgroup that you want to put the PCs and laptop onto. Obviously do this on all of them and make it the same workgroup name each time. Reboot each one after making the change.

Then run the Windows Network Setup Wizard on each PC if they are running Windows XP. If they are not running XP, let us know which version(s) of Windows they are on.

Let us know if that helps