[CentOS] PAE Kernel

>> [root at ns1 log]# rpm -qa |grep kern |sort
>> kernel-2.6.18-194.11.1.el5
>> kernel-2.6.18-194.3.1.el5
>> kernel-2.6.18-194.8.1.el5
> These are stock kernel.

On CentOS 5.x 'yum update' seems to purge all but the latest 3
kernels.  Is there anyway to also do that on CentOS 4.x?  On my CentOS
4.x server I have had '/boot/' fill up and had to uninstall older
kernels.

Matt