In every computer network environment, in order for your pc or laptop to get on the network or internet it needs to be able to grab an address called an IP address from your wireless connection. If it can't pull and address you can't connect. You must first make sure that your internet connection is up by opening a command prompt in windows (windows key + R then type CMD enter) then typing in ping 192.168.1.1 enter. This is the address for your wireless connection if you have a linksys connection. If you don't know your address Google your box make model number and the term "ip address".
When you ping your address what you're doing is asking for a reply back to your computer. This reply establishes that both devices are talking. You should get some type of reply back, if you get a "request timed out or destination unreachable" that means that there is a break in the communications link. The first step is to reset your box by unplugging or turning off the power source, then try to reconnect 4 or 5 minutes later.
Often I will have users get an excellent network signal but not be able to connect. They are frustrated because this is a counter intuitive statement. What this statement is saying is that your connection is established but you haven't entered the right keys to access the kingdom. The problem really lies in the SSID or WEP key. The SSID is your network name and the WEP key is the secret key set by the network administrator to allow access to your wireless network. To set your WEP key follow the link at the bottom of the article on how to set a wireless key. If any of these are wrong that means that though your connection is excellent, your key card doesn't work, hence, no access, but hey your connection is excellent. Lol.
Another issue that occurs often is that if you're bringing home a laptop from work and you're having issues connection to your wireless network, one of two things could be causing the problem.
The first is that your LAN settings are configured to be on your work network and not your home network and two your wireless card is not enabled. To change your LAN settings open up your browser, click TOOLS-->INTERNET OPTIONs-->CONNECTIONS--> LAN SETTINGS. Then uncheck the box that says "USE PROXY SERVER FOR LAN". Click ok and try to reconnect. Just remember to recheck it when you get back to work. To check to see if your wireless card is enabled, RIGHT CLICK "MY COMPUTER"-->PROPERTIES-->HARDWARE-->DEVI... MANAGER. From there find your wireless network card. If its disabled there will be a red X on it. To enable it right click the icon and click enable...