First, make sure your laptop is 'not' connected to the modem/router via an Ethernet cable and follow the steps:
1. Go to "Control Panel".
2. Next go to "Network and Internet" and then "Network and Sharing".
3. Now click on "Manage Wireless Networks".
4. On this screen, remove all wireless connections by "right clicking" on it and select "Remove network" from the drop down menu.
5. After doing this, close the oepn windows and reboot the computer.
6. Once the computer is fully reloaded, scan for the "Wi-Fi networks".
7. Click on the available network that you want to access and select "connect".
8. It takes a moment, but then you will be asked to give a password for your Wi-Fi connection. Type in the password and click the "connect" button.
It should now be connected.
NOTE: If this doesn't work, you may want to reset your modem/router, and then once it is fully loaded again, repeat the above steps. And yes, even if other devices can connect to it, sometimes it needs to be restarted to make it work with a single device.