Wireless signal but no connection

I own a dell 1501 laptop and recently the internet stopped working. It says that the signal strength is excellent but that there is limited or no connectivity. My desktop is currently hooked up directly to the router and i receive the internet just fine. However when i tried hooking up the laptop to the router using an Ethernet cable still nothing, I've restarted the computer, I've turned the router off for half and hour that turned it back on still nothing. The only thing i can think of is that the dell network assistant has expired but i'm not sure if that has anything to do with it, and if it did I'm not sure what to do. Any help that you can extend would be appreciated. Thanks