SUCCESS!
Thanks, Maroon, Raccoon, and Kap.
Your information gave me a greater understanding of my computer.
Here's what I did:
() I closed mIRC.
() I went to c:\users\username\appdata\roaming\mirc and made a backup of mirc.ini
() I opened mirc.ini with Notepad
() It was easy to find all the terms I searched for since the day I bought mIRC.
() I deleted all of them (except the n0= just to be safe).
() I saved mirc.ini
() I loaded mIRC. VoilĂ ! The Channels List search box was cleared of all my old unwanted terms!
Thanks again!