You do not need static IP addresses.

XP machines have a workgroup name and a computer name. You can change both from
My Computer/Properties. They have to reboot for the new names to take effect.
All the computers should have the same workgroup name, and it should not be the
default. Call it ziffnet or something.

To have a shared folder on a Linux system you need Samba.

However, you really only need one share somewhere on the network to be able to
move files around.