You can get a router (Linksys, SMC or Netgear) for chicken-feed money these days- well under $100.00, especially as you already have a hub and thus don't need hub function in the router.
Do that, and you'll avoid issues of overhead on the ICS-server, you'll avoid having to have 2 NICs in the ICS box, you don't have to have the ICS server running all the time to allow access for the other machines.
It's just a better and more-stable solution all 'round.
If you need advice on this topic, go to http://www.dslreports.com
and select the "Networking" forum- there is lots of good and well-documented advice there, including numerous threads on just this topic. You'll find all the info you'd ever need there.
...three miles from BRONS, clear for the ILS one five approach...