Can you send your /etc/yum.conf and /etc/yum.repos.d/CentOS-Base.repo files.
Sure. Here are the contents of both:
------------ /etc/yum.conf ----------------
[main] cachedir=/var/cache/yum debuglevel=2 logfile=/var/log/yum.log pkgpolicy=newest distroverpkg=centos-release tolerant=1 exactarch=1 retries=20 obsoletes=1 gpgcheck=1
# PUT YOUR REPOS HERE OR IN separate files named file.repo # in /etc/yum.repos.d
[main] cachedir=/var/cache/yum debuglevel=2 logfile=/var/log/yum.log pkgpolicy=newest distroverpkg=redhat-release exclude=webmin installonlypkgs=kernel* #kernel-smp kernel-hugemem kernel-enterprise kernel-debug kernel-unsupported kernel-smp-unsupported kernel-hugemem-unsupported tolerant=1 exactarch=1
[dag] name=Dag RPM Repository for Red Hat Enterprise Linux baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag
[base] name=CentOS-$releasever - Base baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/ #baseurl=http://public.planetmirror.com/pub/caosity/centos-4/$releasever/os/$basearch... #baseurl=http://mirror.pacific.net.au/linux/cAos/centos-4/$releasever/os/$basearch/ gpgcheck=1
#released updates [update] name=CentOS-$releasever - Updates baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/ #baseurl=http://public.planetmirror.com/pub/caosity/centos-4/$releasever/updates/$bas... #baseurl=http://mirror.pacific.net.au/linux/cAos/centos-4/$releasever/updates/$basear... gpgcheck=1
#packages used/produced in the build but not released [addons] name=CentOS-$releasever - Addons baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/ #baseurl=http://public.planetmirror.com/pub/caosity/centos-4/$releasever/addons/$base... #baseurl=http://mirror.pacific.net.au/linux/cAos/centos-4/$releasever/addons/$basearc... gpgcheck=1
#additional packages that may be useful [extras] name=CentOS-$releasever - Extras baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/ #baseurl=http://public.planetmirror.com/pub/caosity/centos-4/$releasever/extras/$base... #baseurl=http://mirror.pacific.net.au/linux/cAos/centos-4/$releasever/extras/$basearc... gpgcheck=1
#packages in testing #[testing] #name=CentOS-$releasever - Testing #baseurl=http://mirror.centos.org/centos/$releasever/testing/$basearch/ #gpgcheck=1
------------ /etc/yum.conf ends----------------
------------/etc/yum.repos.d/CentOS-Base.repo ----------------
[base] name=CentOS-$releasever - Base baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/ gpgcheck=1
#released updates [update] name=CentOS-$releasever - Updates baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/ gpgcheck=1
#packages used/produced in the build but not released [addons] name=CentOS-$releasever - Addons baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/ gpgcheck=1
#additional packages that may be useful [extras] name=CentOS-$releasever - Extras baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/ gpgcheck=1
#additional packages that extend functionality of existing packages [centosplus] name=CentOS-$releasever - Plus baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/ gpgcheck=1 enabled=0
#contrib - packages by Centos Users [contrib] name=CentOS-$releasever - Contrib baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/ gpgcheck=1 enabled=0
#packages in testing [testing] name=CentOS-$releasever - Testing baseurl=http://mirror.centos.org/centos/$releasever/testing/$basearch/ gpgcheck=1 enabled=0
------------/etc/yum.repos.d/CentOS-Base.repo ends ----------------