Set the workgroup to match your Windows machines (usually WORKGROUP or MSHOME), add a share for a folder, and give each user a Samba password with smbpasswd -a. Restart Samba and the share should appear in My Network Places.

If Windows XP can't see the server after Service Pack 2, check that File and Printer Sharing is allowed in the Windows Firewall. Tom's talk at the October meeting will go through the whole setup.