[CentOS] "yum update" did not update kernel on one box

This morning, I did "yum update" on my wife's box. It did not update the
kernel. I ran the command again, and there is a response that no updates
are available. Her box is a Compaq Evo D300v Celeron. During the past
couple of days, when I did "yum update", on my daughters box and mine
(Dell Dimensions), the kernel was updated and in the GRUB menus now,
there are two (2) Linux kernels to choose from, as well as the Win XP
option, since these are all dual boot boxes. How can I update the kernel
on the Compaq Evo so it has an up to date kernel? TIA!