I was unable to log in to MIRC- the message was " Yoiur nick is not registered" I then paid and upgraded to the latest 6.21 and there is no register option under help.
This has nothing to do with whether mIRC is a registered copy or not. You were receiving messages from the channel services on the server you were joining. I haven't seen any servers that don't let you join if your nick isn't registered, but I haven't been on many different servers. If you got this message when trying to join a channel, then you'd need to register your nick to get into that channel. Try joining another channel and see if you have the same problem.
And to get help registering your nick (this is free), go to the #help channel on the network you're using.