I
use and recommend xchat, a multiplatform irc client. There are
several versions available for windows and only the official build by zed himself requires registration after 30 days. The other versions are free but might lack certain features.
Xchat is sriptable through various programming langues. mircscript is
not supported; but perl, python, tcl, javascript, lisp, ruby, c (and one more) are. Most scripts require a language plugin, with most scripts being written for perl, then python. There are tcl scripts as well, and, no, you cannot use eggdrop scripts with in xchat.
What IRC client do you use? The looks can be changed by gtk themes and internal configuration of colors and events, and it gets complicated quickly. The screenshot above shows what my xchat looks like. I have attached the corresponding config files (you will need to change them!)