Automatically prefer Ethernet over WLAN

You can set your laptop to "prefer" the Ethernet connection over the wireless. TechNet has a quick overview:

The short answer is that Windows (Vista, 7, 2008, and I’m pretty sure XP and 2003 does as well) [or should do] this by default. The key here is the network interface metric. When you have more than one default gateway defined [...] then the internet bound packets go out the interface with the lowest metric.

[...] You can, of course, permanently alter your metrics by editing your TCP/IP settings on your network adapter’s advanced settings.

[...] You should know that Vista made a change to how we handle existing sockets – after plugging in, connections will not be switched over, you must re-establish the connection in order to make use of a wired connection. For example, if you’re downloading something from a website and realize that it would go faster by plugging in, you’d have to cancel and start over after plugging in. This is a change from XP and 2003.

For how to change these settings, have a look at this Microsoft KB article.

The wireless network is not entirely disabled, but windows is already configured to prefer your wired network when available. This happens via the routing table. Your routing table will have an entry for both interfaces, but the metric for routes on the wired interface has a lower default than routes on the wireless, such that the wired network is checked first when evaluating where to send a packet. You can view your routing table by opening a command prompt and entering route print.

I found a different MS Support article helpful fixing this issue in Windows 7.

It basically explains that you can:

1. Go to the Start menu.
2. Type view network connections in the Search programs and files box.
3. Choose View network connections in the search results.
4. Press Alt and go to the Advanced Options > Advanced Settings... menu item.
5. In the Advanced Settings window that opens, look for the Connections list at the top of the Adapters and Bindings tab, and use the up/down arrows to the right of it to change the priorities of your connections (from highest priority to lowest priority).
6. Click OK to save your changes.

Below is a screenshot of a typical Advanced Settings window with a connection selected in the Connections list and the up/down arrows to the right of the list enabled accordingly:

A good internet connection manager is Lenovo Internet Connection (AKA Lenovo Access Connections). With this tool you can create profiles, and have them in an order of preferred networks (i.e. wired over wireless, etc). The profiles you create can be exported and used on other computers.

-Good Luck