[CentOS] lost CentOS repositories from yum

From: Sagar Koirala <sagar.koirala at gmail.com>
> I was using yum, which was working very well. Then I decided to try
> yumex, and installed yumex, which again worked fine. But, after that,
> when I came back to use console yum, it started giving error messages.
> So, I removed yumex and tried, in vain. Then I removed yum, and
> installed it with rpmforge repository.
> It works fine, but I only have rpmforge repository. How can I add
> CentOS repositories like Addons, Extras, etc back to my yum?

Maybe reinstall yum from the rpm file from CentOS?
Or at least extract the /etc/yum.repos.d/CentOS-*.repo

JD