There are plenty of reasons why that could be asked. Do you save your emails... forever? Maybe he registered mIRC 4 years ago. Obviously, he would have deleted the email since then. But, he took the time to write the registration code down on a piece of paper. Now he got a new PC and he wants to register mIRC. So he needs to know where to enter the information since he no longer has the email explaining it.
I'd say that's a very likely scenario.
