Remove and reinstall the Wireless software, then check your connection security codes carefully... download the latest version of the setup software from the manufacturer.
There are really too many options for us to give a simple explanation in the space available.
Wireless is one of those tricky ones. Once you fully understand it on a given machine, it is very simple. But until you understand it, the frustration level is extremely high... So do your home work with a lot of reading of materials related to that laptop and to the software and connection that he has installed. It can be a quick fix, but usually is not.