Administering Wireless Network sharing a Alltel USB Internet Connection

I have situation in which a Desktop PC and Laptop both using Windows XP OS are to be networked for file sharing. However, the catch is the client is using a Alltel USB Internet Service Card. The USB card may be plugged into either PC, I’m thinking the desktop as the host and I was hoping to share the internet connection between PC’s so both have internet access. The Client wants the connection to be wireless so they can roam with the laptop. Any Suggestions as to how to set up this network for file sharing and sharing internet access would be appreciated.

Thanks,

Steve