It depends on what you are trying to do. Are you trying to stop users from coming in a channel if they don't have a registered version of mIRC? because there are many other IRC clients. You could make it possible by forcing users to DL an AddOn that would reply to a special CTCP request that would send encrypted information, but I don't recomend it.
If you are, on the other hand, trying to check if mIRC is registered on the current computer, all you have to do is look at the registry settings (I would recomend a DLL rather than WScript) or you can even use a DLL to check if the "Register mIRC" menu option exists.
Anyway, just some thoughts.
