Ok the first step is to network these computers, (basically this allows you to share files and devices over a network and be able to see the other computers shared files from your pc)
If you run Windows XP Professional, open "My Computer" and select Tools and then Folder Options. Under the View tab, go to the advanced setting window. Scroll down until you see the option to "Use Simple File Sharing." Uncheck it, if it is checked, Now, click Apply, then OK, otherwise the change will not occur. Go to your Start menu, select Control Panel. Find the Network and Internet connections button. In the Network Connections panel, right-click your Ethernet card (usually referred to as "Local Area Connection"). Under the General Tab, make sure that "File and Printer Sharing For Microsoft Networks" is clicked.
Now, you'll go back to the main Control Panel and select Performance and Maintenance, and select System (if you are using Classic View, select System). In the window that opens, select the "Computer Name" tab, and down three-quarters of the way, click on the Change button. From here, make sure that the Workgroup name is XXXXX XXXXX for all computers. Windows XP Home uses MSHOME, while XP Pro uses WORKGROUP. I'd leave it as WORKGROUP, but you could switch it to your last name or anything else, so long as you use the same workgroup name on all the systems. You will need to reboot the computer now to make the changes.
On the Vista computer, you're going to click on the Start menu and type "system" in the Search Box. Click on System when it appears in the menu. In the Computer Name Domain and Workgroup Settings, you'll see the name of the workgroup that Vista has set up already. Change that name to whatever you've set on the XP systems. To change it, simply click on Change settings. Vista will pop up the now familiar (or obnoxious) UAC (User Account Control) warning. Select Continue. From here, change the workgroup name to the one you've selected. Make sure you've picked the Computer Name tab. Click on Change next to the words "To rename this computer or change its domain or workgroup, click Change..." At the bottom of the system properties window, you will find an option called "Member of." Choose Workgroup. The default name should already be WORKGROUP. You can change it to the one you want to use. Click OK. Now, reboot the computer. Do not choose Domain. That is mainly in use in corporate environments or if you are running a Windows server in your house with a domain controller. That, of course, is not a likely scenario for the average home user.
Reboot the Vista machine
Once Vista is configured, and all of the other computers are on the network, they should be able to see each other
Now we can go about sharing the printer,
Here is a guide that will show you how to share your printer and how to connect the other computers to this shared printer.
Hope this helps,