Here is how to share your Wi-Fi signal using a single card, under Windows 7 or 8:
First of all, learn how to open Command Prompt with Administrator privileges. Go to Start menu, right click on Command Prompt and select ‘Run as administrator’. If you don't have Command Prompt in your Start menu, then type cmd
then right click as above.
In the Command Prompt window, enter the following command:
netsh wlan show drivers
If you see line: Hosted network supported : Yes
it means your Wi-Fi card will work, and you can share your Wi-Fi signal easily.
Now see Setting up a virtual router in Windows 7
This should work with a lot of Wi-Fi cards, but if your card doesn't have Hosted network support, I recommend one of these