I just did a quick google search.
http://www.geekstogo.com/forum/How-to-disable-wireless-when-Ethernet-plugged-t1648.htmlstart -> control panel -> network and internet connections icon -> network connections icon -> advanced menu -> Advanced settings... -> in the Connections: box, move the Local Area Connection up (before Wireless Network Connection). This will make the Local Area Connection profile take precedence over the Wireless Network Connection profile -> REBOOT.
Or a paid way.
http://www.wirelessautoswitch.com/Downloads.aspxhttp://www.wlanbook.com/bridgechecker/