1. Enable ICS on the Windows XP computer.
2. Set all other computers to "obtain IP address automatically".
3. Reboot everything.
That should be about it.
The client computers should have IP addresses of the form 169.254.x.x with a netmask of 255.255.0.0 - this is the range reserved by Microsoft for APIPA, Automatic Private IP Addressing, which is available on Windows 98 and up.
Turn NetBEUI off, for goodness' sake! That's not a Real Man's network protocol!