At current this is not possible on Android based devices.
You can tether your phones internet connection to your PC in order to use your mobile networks data connection on your computer, but you can't go the other way around.
If your PC has a wireless card (all modern laptops do) and gets its internet over a wired ethernet cable, all you have to do is turn on Internet Connection Sharing. ICS will then turn the PC's wifi card into a wireless access point, complete with SSID, optional password, etc. Your phone can then connect to the PC's wifi network and piggyback over the PC's wired Internet connection.