Steps to connect two PCs together with a wireless ad-hoc connection, and share the tethered internet from the host machine.
This applies to Windows 7, and both computers had ASUS Wireless-N150 USB adapters, linked here:
http://www.asus.com/Networks/Wireless_Adapters/USBN10/
Disable the ethernet LAN on the host.
Establish the Internet on the host.
Open the Network and Sharing Center, Add a connection in Manage Wireless Networks, choosing Create an Ad-Hoc Network.Â
Give it a name, turn off security, and create the new network. (The Save this network checkbox is optional.)
It should then ask you if you'd like to turn on Internet Connection Sharing, which you do.
The host computer needs to be "connected" to the ad-hoc network first, before it will broadcast itself to other users. Once it's connected on the host, it can be seen in the wireless network list as "Waiting for other users...". Then the second computer should see it, be able to connect to it, and be able to use the Internet.