What files do I delete to uninstall glib?
Simple. You just don't. Glibc is the core library even the most basic Linux apps need and w/o it won't even run. What's the reason you're asking? Did something go wrong upgrading?
Well, you *could* get rid of Glibc like in downgrading it, but that involves a Linux rescue CD with a previous "known good" version of Glibc on it and make sure the tools on your HD aren't wired to like Glibc-2.3 when you're thinking about installing 2.1. Compatibility doesn't mean everything will run smoothly. Query, list the contents of the glibc rpm's, and make a backup. Boot the rescue cd, install or unpack the libraries, rerun ldconfig and cross your fingers it'll run once you rebooted. Like performing open heart surgery, listening to New Age, or drinking mescal, this is a task you better thing about twice.
In Linux if you want to install a new version of something (x-chat in this case) do you have to uninstall the old version?
Upgrading could do.