I use cable internet (router wired to my PC) and my PC has a wireless network card.
How can I connect my laptop to the PC in order to use the cable internet?
You can use Internet Connection Sharing. Go to Network connections on your PC. If you are using 7 or Vista, use the "Setup a new connection or Network" and select "allow others to use this internet connection."
If you are using XP, find the wired connection, RClick and Properties. Select the Sharing tab and click the check box for "allow other network users. . ." Select the Wireless Connection as your home network connection.