if your wifi adapter is already connect, you cannot without another adapter, if you are connected via lan and your wifi adapter is idle, these steps work from chainzsaw on this forum
http://www.tomshardware.com/forum/26463-63-internet-sharing-wifi-laptop
◦1
Plug the wired connection Ethernet cable into the Ethernet port on your laptop.
◦2
Press the "Start" button. Choose "Control Panel" from the "Start" menu.
◦3
Double click the "Network and Sharing Center" icon.
◦4
Choose "Set Up a New Connection" under the "Tasks" menu on the left-hand side of the screen.
◦5
Choose "Set Up a Wireless, Ad Hoc Network" from the available options.
◦6
Name your network and choose a password.
◦7
Press the button that says, "Turn on Internet...