when i had the wii i plugged it in and it worked fine after i entered my WEP key it worked fine.
Go to the wii home menu, then options in the bottom left corner of the screen, then settings on the right
the go to page 2 (click the right arrow) > then internet > connection.
click connection 1 > click wireless connection > search for an access point, it will search and come up with a list of all available connections, click on your router.
it should now ask you for your WEP key, enter it and press ok.
it hould test the connection and give you an update option, click yes and let it update itself.
go back to system settings then Wii connect 24 and click yes and make sure thats switched on and click confirm.
you should now be ready to rock and roll wirelessly.
if that doesnt work then go to
http://www.nintendowifi.com/ and check and see if your modem is supported by the wii.
you should also log in to your router and make sure it is switched on to send a wireless signal.
Hope that helps
T1