Um, I accidentally put the wrong e-mail to register for my name...

what should I do???

First, you can slap yourself silly with a baseball bat.

Then, assuming you still wish to use mIRC - try this: http://www.mirc.com/reglost.html

do you mean to register your nickname? best to ask in a help channel on the network you registered on, (check their website or MOTD, all the stuff that scrolls past when you connect for channel names).