If you have your registration code for years already but it no longer seems to work in mIRC 6.3x, no worries; contact khaled and ask for help. Khaled removed some old registration code validation routine from mIRC. Some very old registration codes still used/needed this routine to work. If you happen to have one of these old reggy codes Khaled will provide you with a new one.
If you forgot your reggy code, or if you're unsure about it, use the RegLost page at http://www.mirc.com/reglost.html
to get your reggy code re-sent.