|If there is no wireless adapter on your PC, then it must be at least equipped with network adapter. You can enable Internet Connection Sharing as shown here on laptop, after that connect laptop to PC with crossover network cable and share Internet connection with PC. |
However the best and common way is to get a wireless router and set up a simple wireless network to share Internet. This is wireless network setup tutorial, you might take a look if you are interested.
Hope this helps.