CentOS 4 is no longer supported by the developers and we do not recommend you install it. If you have a special case which requires CentOS 4, you will find that yum will not update or perform installs because the repository URL’s are no longer valid.
To make yum work with vault.centos.org, edit your :
/etc/yum.repos.d/CentOS-Base.repo
to have these lines:
[base]
name=CentOS-$releasever - Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://vault.centos.org/4.9/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
priority=1
protect=1
#released updates
[update]
name=CentOS-$releasever - Updates
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://vault.centos.org/4.9/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
priority=1
protect=1
yum update, yum install, etc. will now work.