root@monkeynut:~ >rpm -qa |grep kernel
kernel-xen-2.6.18-8.el5.x86_64


root@monkeynut:~ >yum erase kernel-xen
Loading "installonlyn" plugin
Setting up Remove Process
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Package kernel-xen.x86_64 0:2.6.18-8.el5 set to be erased
--> Running transaction check

Dependencies Resolved

=============================================================================
 Package                 Arch       Version          Repository        Size
=============================================================================
Removing:
 kernel-xen              x86_64     2.6.18-8.el5     installed          73 M

Transaction Summary
=============================================================================
Install      0 Package(s)
Update       0 Package(s)
Remove       1 Package(s)

Is this ok [y/N]: y
Downloading Packages:
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
grubby fatal error: unable to find a suitable template
grubby: doing this would leave no kernel entries. Not writing out new config.
  Removing  : kernel-xen                   ######################### [1/1]

Removed: kernel-xen.x86_64 0:2.6.18-8.el5
Complete!
root@monkeynut:~ >rpm -qa |grep kernel
    
root@monkeynut:~ >rpm -q yum
yum-3.0.5-1.el5.centos.2.noarch