unable to go wireless connection

If possible try connecting to the wireless network using another computer to verify the modem / router config is correct. I assume you already did this since you said its setup correctly.

On the laptop go to the network connections folder and disable then enable the network connection. You can do this by right mouse click on the wireless connection.

Click Start --> Run --> type "cmd" (without the quotes anytime you see them). At the prompt type "ipconfig /release" and press enter. Now type "ipconfig /renew" and press enter.

If there is any wireless security (like WEP, WPA, etc.) make sure you entered the key correctly when you were asked for it the first time you connected to the network. To make sure go back to the Network Connections folder right mouse click the wireless connection click properties and go to the wireless network tab. You can remove the network so it will prompt you again for key or password (if any).