I assume you’re running WinXP Home and you haven’t set up a Workgroup!

If so, firstly, set up a workgroup by right-clicking My Computer > Properties > Computer Name and change the default Workgroup Name to something more meaningful in your household, also make the Computer Name recognisable, e.g. MainPC or IBMPC. The computer should reboot.

Now identify the folders/files you want to share and right-click them and select share and read or read/write access. A little hand should appear under those that are shared. Alternatively, drag the files you want to share to Shared Folders.

Repeat this on all PCs, use the same workgroup name but, of course, a different computer name.

To see or copy files, go to Start > My Network Places and the computers/folders/files should appear. Using Explorer drag them from one PC to the other.

Windows firewall is normally set to allow file and printer sharing but if you have a third-party firewall make sure that it allows access so that each machine can talk to the other(s).

Share a printer, here http://www.microsoft.com/windowsxp/using/networking/maintain/printers.mspx