Given that the laptop is old, it might be that the laptop wireless adapter does not support newer standards far as the security on the router. You could test this by temporarily disabling the security on the wireless router and see if the laptop will then connect.
Beyond that we need to know the following:
Make and model of the laptop?
Make and model of the wireless adapter?
Current operating system?
Beyond that we need to know the following:
Make and model of the laptop?
Make and model of the wireless adapter?
Current operating system?
