There is an updated kernel available for CentOS-3.1
https://rhn.redhat.com/errata/RHSA-2004-188.html refers.
Updated files are :-
Common Files
i386/updates/RPMS/kernel-BOOT-2.4.21-15.EL.c0.i386.rpm i386/updates/RPMS/kernel-doc-2.4.21-15.EL.c0.i386.rpm i386/updates/RPMS/kernel-source-2.4.21-15.EL.c0.i386.rpm
athlon specific
i386/updates/RPMS/kernel-2.4.21-15.EL.c0.athlon.rpm i386/updates/RPMS/kernel-smp-2.4.21-15.EL.c0.athlon.rpm i386/updates/RPMS/kernel-unsupported-2.4.21-15.EL.c0.athlon.rpm i386/updates/RPMSkernel-smp-unsupported-2.4.21-15.EL.c0.athlon.rpm
i686 specific
i386/updates/RPMS/kernel-2.4.21-15.EL.c0.i686.rpm i386/updates/RPMS/kernel-smp-2.4.21-15.EL.c0.i686.rpm i386/updates/RPMS/kernel-hugemem-2.4.21-15.EL.c0.i686.rpm
i386/updates/RPMS/kernel-unsupported-2.4.21-15.EL.c0.i686.rpm i386/updates/RPMS/kernel-smp-unsupported-2.4.21-15.EL.c0.i686.rpm i386/updates/RPMS/kernel-hugemem-unsupported-2.4.21-15.EL.c0.i686.rpm
source rpm
i386/updates/SRPMS/kernel-2.4.21-15.EL.c0.src.rpm
These are available at http://mirror.centos.org/3.1/ and should be on all mirrors within a few hours.
To update to the latest version 'yum update kernel' should be sufficient.
Lance