Red Hat has released version 5.4 of RHEL. One of the new feature of the fourth major RHEL 5 update is the support of KVM (Kernel-based Virtual Machine) virtualisation. RHEL5 will continue to support Xen virtualisation, but it looks like Red Hat intends to go for KVM in the long run. List of supported KVM guest systems includes all the currently maintained RHEL versions as well as Microsoft Windows XP, Windows Server 2003 and Windows Server 2008.