First step is to try it without any wifi security, disable any software firewalls, and enable SSID broadcast in the router. Once you get it working then move to instigating wifi security and configuring the software firewall.
It's also worth doing a quick check by ethernet cable to see if the laptop works by wire. Disable the wireless connection in network connections - right click, while doing this.
Without any security it's also good to turn the wireless off in the router when you're not using it.