CentOS 4 offers both yum and up2date to do updates of the operating system. You can use either or both of these to manage your updates.
Prior to using yum, you must import the RPM-GPG-KEY for CentOS-4 like this
rpm --import /usr/share/doc/centos-release-4/RPM-GPG-KEY
The following files are changed from the upstream RPMS. All changes are trademark and look/feel related unless otherwise noted under the specific RPM.anaconda-10.1.1.19-1.centos4.i386.rpm
anaconda-help
anaconda-product
anaconda-runtime
createrepo
centos-release
centos-yumconf
dhclient
dhcp
dhcp-devel
firefox
firstboot
glade2
gnome-desktop
gnome-desktop-devel
gnome-session
httpd
httpd-devel
httpd-manual
httpd-suexec
indexhtml
initscripts
mod_perl
mod_perl-devel
mod_ssl
mozilla
mozilla-chat
mozilla-devel
mozilla-dom-inspector
mozilla-js-debugger
mozilla-mail-1.7.8
mozilla-nspr-1.7.8
mozilla-nspr-devel
mozilla-nss
mozilla-nss-devel
redhat-artwork
redhat-logos
rhn-applet
squirrelmail
up2date
up2date-gnome
yum
sqlite
sqlite-devel
python-elementtree
python-sqlite
python-urlgrabber