There are two basic operations, 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 Vista computer to a workgroup by right-clicking Computer > Properties > Change Settings then change Computer Name and Workgroup Name. Make the computer name meaningful to aid recognition. The computer should reboot.
To share a folder, right-click it > Share, type 'Everyone' (not the quotes), click Add and set the drop down Permission Level alongside Everyone to either Reader or Co-owner then click Share at the bottom. Two little people should appear on the icons of those that are shared. Alternatively, drag the folders you want to share to the Public folder.
Make sure in Control Panel > Classic View > Network and Sharing Center you have Network Discovery, File Sharing and Public Folder Sharing set to ‘On’ and, if you‘re not using passwords set Password Protected Sharing to ‘Off’, unless you want to set up identical usernames and passwords on all computers in your network. If you have it on, you will be asked for a username and password when you try to access a Vista computer from an XP computer.
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(s).
To see or copy files click the Windows Orb (Start) > Network (My Network Places in XP) and the computers/folders/files should appear. Using Windows Explorer drag them from one PC to the other.
SHARE A PRINTER
On the machine that the printer is connected to, go to Control Panel > Printers, right-click the printer, click Sharing, check ‘Share this printer’. On the other machine(s) go to Control Panel > Printers > 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.