You need to go to "my computer" and then "My Network Places" and then "Set Up a Home Or Small Office Network".
Go through the setup process of this on each machine. If they are all XP, ignore the last request to create a CD/Disk.
Once that is done, you can share folders and printers between machines.
On the machine with the printer attached, click on the printer in "Printers and Faxes" in the "Control Panel". Right click and select "share this printer".
On the other machines, go to "printers and faxes", and select "add printer", and then "network printer". Follow the setup for this.
Bes bet is to get a networkable printer or a print server, you then dont need to leave a machine on to print.