There are a number of things that can cause connection problems.
Follow these steps to solve several common problems associated with wireless connections:
Ensure that if your laptop has a switch to turn on the 802.11 wireless network adapter, that it is turned on. This switch may be located on the side or front of the computer.
Make sure that the wireless adapter is not disabled. Click Start > Control Panel. The Control Panel has two views. In Category View click the Network and Internet Connections icon.
In Classic View click the Network Connections icon.
In the Networks Connections screen check the Wireless Network Connection status, if it reads Disabled, right click on the icon and click Enable.
In the Networks Connections screen, right click on the Wireless Network Connection icon and select Properties
In the Wireless Network Connection Properties dialog box click the Wireless Properties tab. Ensure the Use Windows to configure my wireless network settings checkbox is checked. Click the OK button.
Use Wireless Auto Configuration to configure wireless network settings. Right click on the Wireless Connection icon in the Notification Area.
Select View Available Wireless Networks.
The Wireless Network Connection window will appear. Select the wireless connection you want to connect to from the list, then click on the Connect button. If no connections appear in the list click the Refresh network list link to search for wireless connections.
Check to see if the desired wireless network appears in the network list. If the wireless connection is not appearing in the Available Network List you may be outside of the broadcast range of the network. Try relocating to get a stronger signal.
Check to see if a wireless warning icon appears in the notification area.
You can click on this image to get more information and remedies to correct the problem.
If you have connected to the network before, but this time the connection has failed, right-click on the wireless icon and click Repair