[CentOS] Yum Troubles

>> Um, er, what now?
>
> Delete obsolete kernels that are still on your system.

I see this:

[root at serv cron.daily]# rpm -qa | grep kernel -i
kernel-smp-2.6.9-42.0.8.EL
kernel-2.6.9-55.EL
kernel-smp-2.6.9-55.0.2.EL
kernel-smp-2.6.9-55.0.6.EL
kernel-2.6.9-55.0.12.EL
kernel-smp-2.6.9-67.0.1.EL
kernel-utils-2.4-13.1.105
kernel-smp-2.6.9-67.0.4.EL
kernel-2.6.9-67.0.4.EL
kernel-smp-2.6.9-67.0.7.EL
kernel-smp-2.6.9-67.0.15.EL
kernel-smp-2.6.9-42.EL
kernel-2.6.9-42.0.10.EL
kernel-smp-2.6.9-55.EL
kernel-2.6.9-55.0.2.EL
kernel-2.6.9-55.0.6.EL
kernel-2.6.9-55.0.9.EL
kernel-2.6.9-67.0.7.EL
kernel-2.6.9-67.0.15.EL
kernel-2.6.9-67.0.20.EL
kernel-smp-2.6.9-67.0.22.EL
kernel-2.6.9-67.0.1.EL
kernel-2.6.9-42.EL
kernel-2.6.9-42.0.8.EL
kernel-smp-2.6.9-42.0.10.EL
kernel-smp-2.6.9-55.0.9.EL
kernel-smp-2.6.9-55.0.12.EL
kernel-smp-2.6.9-67.0.20.EL

Do I just "rpm -e" the older ones?  Which ones dont I remove?

I see something like this in grub.conf:

default=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.9-67.0.20.EL)
        root (hd0,0)
        kernel /vmlinuz-2.6.9-67.0.20.EL ro root=/dev/VolGroup00/LogVol00
        initrd /initrd-2.6.9-67.0.20.EL.img
title CentOS (2.6.9-67.0.20.ELsmp)
        root (hd0,0)
        kernel /vmlinuz-2.6.9-67.0.20.ELsmp ro root=/dev/VolGroup00/LogVol00
        initrd /initrd-2.6.9-67.0.20.ELsmp.img
title CentOS (2.6.9-67.0.15.ELsmp)
        root (hd0,0)
        kernel /vmlinuz-2.6.9-67.0.15.ELsmp ro root=/dev/VolGroup00/LogVol00
        initrd /initrd-2.6.9-67.0.15.ELsmp.img
title CentOS (2.6.9-67.0.15.EL)
.......................

Thanks

Matt