How can I make Windows prefer my wired connection?

Looks like Windows (XP, Vista, 7) are supposed to do this automatically. Windows uses the lowest 'metric' connection. You can manually alter these metrics if it isn't working correctly, but in most cases, wired should be preferred over wireless automatically. Check the source below for more how-to and explanation.

Source

th3dude's answer is great but he doesn't mention a key point in the link he provided.

From the link that th3dude posted: http://blogs.technet.com/b/clint_huffman/archive/2009/04/19/windows-prefers-wired-connections.aspx

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. Here is a good reference:

The Cable Guy Strong and Weak Host Models http://technet.microsoft.com/en-us/magazine/2007.09.cableguy.aspx

Which means that when I am on wireless at work in a conference room and then drop the laptop back on the dock, I have to disconnect (software) from the wireless connection OR disable (hardware switch) the wireless adapter to get back on the wired network.

Hopefully that helps you understand that it is probably not the 'metricing' that is choosing the wireless adapter but rather that Windows no longer auto-switches as it did in XP.

I'm not sure why Microsoft thought this was preferred behavior. I would have preferred a pop-up asking me whether to enable the wired adapter instead at the risk of ongoing downloads and sessions. Windows 7 makes me answer all kinds of other popups.

As explained here:

http://answers.microsoft.com/en-us/windows/forum/windows_7-networking/how-make-win-7-to-prefer-wired-over-wireless/97ae998b-5743-e011-9767-d8d385dcbb12?tab=question&status=AllReplies#tabs

a. Open the Network Connections folder (Start > Run > ncpa.cpl)

b. Right click the desired connection.

c. Click Properties and then click on Internet Protocol Version 4.

d. Click Properties and then click on Advanced.

e. Un-check "Automatic metric".

f. Enter a number between 1 and 9999 for the "Interface metric".