Sometimes laptops will connect over WiFi even when a LAN cable is plugged in. This can be problematic in business environments where the LAN connection is required. To resolve the problem try this:
1. Open the Network Connections folder (Start > Run > ncpa.cpl)
2. Right click the desired connection.
3. Click Properties > Internet Protocol Version 4.
4. Click Properties > Advanced.
5. Un-check “Automatic metric”.
6. Enter a number between 1 and 9999 for the “Interface metric”.