Howto set priority of LAN over the wireless connections
With Windows 7, if both LAN and wireless adapters are enabled, the wireless connection automatically becomes the main connection.
I believe this happens if you connect wireless to the wireless network after you are connected on the LAN, something similar to Last In First Out (LIFO) method :)
You can modify the settings to that your computer retains LAN as the default and main connection, here's how:
Click Start - Control Panel - Network and Sharing Center
Open any folder and enter Control Panel\All Control Panel Items\Network and Sharing Center in the location bar
Click 'Change adapter settings'.
Press alt key to make the menus visible, click Advanced - Advanced Settings.
Move Local Area Connection to the top in the Connections box.
And you're done! now even if your wireless adapter is connected, the traffic will flow through the LAN adapter.