CPU limitation in RHEL 5.x
 

The (30 day trial) version of Red Hat Enterprise Linux available for download at www.redhat.com supports up to 2 CPUs.

My server has a Intel® Quad-Core processor and I am running RHEL 5.2 x86-64 (limited to 2 CPUs). So that means the OS is not harnessing the full power of the CPU. Am I right?

Would it be a good idea to use CentOS 5.2 x86-64 instead if I don't want paid support? (for harnessing the full power of the CPU)?

yes.

You can use CentOS-5.2 or Scientific Linux-5.2 instead...if you do not want paid support

Thanks for your reply.