Home Network :: Double Protection Network Configuration?

I have a problem with my home network/internet - I have a working wireless network that I have used for some time now and it works just fine. the problem is that internet restrictions where I live require me to register each unit to the building network before I can gain access to the internet. My caretaker told me today that normally, I only should register my primary computer and the wireless router to be able to use the internet freely. However when a new laptop appears( I have a guest), I can easily connect it to my own wireless, but it can't use the internet, as if it needed to be registered again. I ran out of registration codes and I really would like to have freedom i connection opportunities. The caretaker said that the system gives every registered unit a "fake" IP, so after giving it to mu router, all other units connected through that router should have unlimited access. Is my network configured in a wrong way? I don't know how to ask this in a more simple way... I just want to be able to connect a friends laptop to the net with just my local password, which isn't happening.