Electrif says:

1. What router do you have? If it’s a Dead Link (DLink), replace it with a Linksys.
2. Go to My Network Connections (assuming you have Windows XP), click “view network connections”, right click on the your wireless connections then click “properties”. In the box, you’ll see some options with boxes (probalbly with checkmarks in them) the bottom of those options should be “Internet Protocol”, double-click that. Click on “Obtain IP Automatically” and “Obtain DNS server address automatically” if you haven’t already. Click OK then close the other box (the one your were previously).
If that doesn’t work, go back to where you were, right click your wireless connection in Network Connections then click “Properties” that bring up the box again. There should be a middle tab (unless your using a Linksys wireless card) call “Wireless Networks”.
In the preferred networks box, delete any names that are in there. Click the Add button.
For the SSID, that is the network name (usually the default name of your router if you haven’t changed it already Ex. Linksys router would be named linksys). check the box the says “Conect even if this network is not broadcasting”.
Note: If you have it password protected, uncheck the box near the bottom that says “The key is provided for me automatically” then put your password or key in the two boxes. If you don’t have a password (open connection) then skip that and leave the box check marked.
Click the Advanced button (not the tab) and check mark the box “Automatically connect to non-preferred networks. Make sure the 1st above option is selected. When your done close that box.
Now, click the Advanced Tab now, click the only button (called Settings) in that tab. A new box will pop-up.
Click the last tab (advanced tab).
There will be at least one option the called something like “Wireless Network Connection”. Click the Setting button near it.
A new pop-up, check mark all the boxes, then click OK. Close out of the other boxes. Wait a minute and if no luck, right click on your wireless connection icon in your taskbar and click “repair”.