I have Centos 3.3 installed on a vmware virtual machine on a AMD Opteron processor.  I upgraded the kernel to version 2.4.21-27.0.2.EL, and now when I boot the system I get the following message:

Cannot open root device "LABEL=/"
Kernel panic: VFS: Unable to mount root fs on 00:00

The server boots fine with kernel-2.4.21-20.  I've change the root=LABEL=/ to use the /dev/sda2, and it did not work.
Does anyone has any ideas what causes the system not to boot?

Thanks. 

Roberto DaSilva