Unable to update Centos 5.3

Unable to update Centos 5.3 using the command, "yum -y update." When doing so, I receive the long message below. I have also tried "yum clean all,"yum clean metadata" and "yum update kernel." The server has 256 MB and my only interest is keeping up with security updates before I get hacked

yum clean metadata
Loaded plugins: fastestmirror
12 metadata files removed
8 sqlite files removed
0 metadata files removed
> yum update kernel
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Excluding Packages in global exclude list
Finished
Setting up Update Process
No Packages marked for Update
> yum update kernel
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Excluding Packages in global exclude list
Finished
Setting up Update Process
No Packages marked for Update

Here is the fix:-
--------------
yum clean all
yum update glibc*
yum update yum* rpm* python*
yum clean all
yum update
shutdown -r now