Firstly put all the computers in the same workgroup then, secondly, choose the folders on each machine that are to be shared. Repeat this on all PCs, use the same workgroup name but, of course, a different computer name for each of your computers.
ADD A COMPUTER TO WORKGROUP
Add an XP computer to 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.
To share a folder, right-click it and select Sharing & Security > Sharing Tab > Share this… and optionally, Allow Network users to….. You only need to share the highest level folder, e.g. not every sub-folder. A little hand should appear under those that are shared. Alternatively, drag the folders you want to share to the Shared Documents folder.
On the machine that the printer is connected to, go to Control Panel > Printers & Faxes, right-click the printer, click Sharing, check ‘Share this printer’. On the other machine go to Control Panel > Printers & Faxes > Add printer and follow the wizard. Bear in mind that the printer and the PC that it’s connected to must be switched on, unless you have a ‘proper’ wireless printer/adapter.
Windows firewall is normally set to allow file and printer sharing but if you have a third-party firewall make sure file and printer sharing is enabled so that each machine can talk to the other.
To see or copy files, click Start > My Network Places and the computers/folders/files should appear. Using Windows Explorer drag them from one PC to the other.