Windows 7 supports a Soft AP mode that can be used to create a more secure sharing environment as it supports WPA2\AES. This works with most WLAN Nics but there may be issues with some older kit.
The steps you need to follow are:
1: Open up an administrator command prompt.
2: Create the SoftAP config:
netsh wlan set hostednetwork mode=allow SSID=PeerWithWPA2 key=WPA2Password keyusage=persistent
3: You will now need to modify your ICS settings to allow sharing from your main internet adapter to this new network. You manage this from the properties->sharing tab of the network adapter that is your primary internet connection. This can be the same WLAN adapter that will be used for the Soft AP.
4: Start the SoftAP
netsh wlan start hostednetwork
5: Connect to this from your other systems just as you would connect to any AP that provides a WPA2 secured SSID
There is a full guide with screenshots available here.