HP puts VT Flag in OS Security

At work we have an HP dc5750 machine that we want to put some HVM VMs on. The processor in the machine is an AMD 4450B that technically supports AMD-V. After installing Xen and booting the machine we found that HVM was not enabled in Xen so we had to go digging around. We looked through all the sensible BIOS options a few times and upgraded the BIOS to the latest version and then finally in frustration looked in the OS Security section and there it was - Virtualization was Disabled.