Do you ever plug in your wired network card while your wireless card is still enabled? Ever wonder how Windows chooses which one to use? Heres how to see the default priorityand how to change it if you want.
Note: theres almost never any reason to change this, as Windows does a good job of choosing the right connection.
Still, if you want to tweak it to work differently, this is how you would do it.
How to See the Current Network Card PriorityYoull need to open up a new command prompt window and type in the following command:
netstat -rn | more
The | more part of the command will make sure that it doesnt go flying off the screen, requiring you to scroll backwardsspeaking of which, you should read the article about 
how to scroll backwards in the command prompt with the keyboard.

At the top of the output youll see the Interface List, and the column on the left-hand side shows the metric of the interface. Youll notice that the loopback interface has the highest priority, followed by my wired Gigabit card, and then my wireless card. 

If youre wondering what all the other cards in the list are about, Ive got some VPN software loaded, as well as VMware Workstation, all of which create virtual adapters that show up in the list.
How to Change the Network Card PriorityTo change the priority, head into Network and Sharing Center and click on the Change adapter settings link on the left-hand sideor you can 
quickly open the network connections list by typing 
ncpa.cpl into the Start Menu search box.

Now that were in here, choose the network card that you want to change the priority for, right-click it, and choose Properties from the menu.

Now select the Internet Protocol Version 4 item in the list, and click the Properties button.

Now click the Advanced button at the bottom of this window
. getting tired of clicking yet?

And now, finally, were at the place where you can make the change. Uncheck the box for Automatic Metric, and then type a number into the Interface Metric textbox. You can consult the list that we found in the command prompt earlier to know what metric to assignyoull probably want to assign it something higher than 1, since thats used for the loopback adapter.

You may want to go ahead and change the priority for your other card as well, just to be sure that it is assigned the proper priority.
Note: again, theres no reason to mess with this setting unless you are actually having a problem.