You should be able to exclude an IP address from the DHCP range in XP (I've done it in 2k3 server, not sure about XP) for your miggy. Try right click my computer -> manage -> ... ok someone with XP in front of them might be able to help ;-)
Anyway, even if you don't exclude an IP from the DHCP range it should still work (just hope the IP you're miggy has "stolen" doesn't get served up by the XP ICS machine :-) )
Then set your gateway to the ICS machine, perhaps DNS too (if it does DNS forwarding.. 2k3 server does).
- Paul
