internet connection problems

My dad's laptop's suddenly stopped connecting to the internet. I had the same problem, and tried doing what I did to fix the problem before(turn off IPv6 Protocol), but that hasn't worked, so we've got no actual idea of how to fix the problem. His laptop's connecting to the router, but he can only get "limited access", yet I'm connected to the same router and have full access.

tl;dr my dad's internets are broke, halp me fix them.

This "limited access" is one of the best examples of Windows' ridiculously uninformative and misleading error messages.

It just means that it did't receive any DHCP offers. So there's something wrong with the computer's network settings or with the network itself between the computer and the router.