If you are using Vmware Technology for your Virtualisation, you may find this information useful.
Taken from Vmware KB Determining if Intel Virtualization Technology or AMD Virtualization is enabled in the BIOS without rebooting (Jul 29 2010). Simplified at my blog Determining if Intel Virtualization Technology or AMD Virtualization is enabled in the BIOS without rebooting (Virtual Machine Journal)
Product Versions affected:
VMware ESX 3.0.x
VMware ESX 3.5.x
VMware ESX 4.0.x
VMware ESXi 3.5.x Embedded
VMware ESXi 3.5.x Installable
VMware ESXi 4.0.x Embedded
VMware ESXi 4.0.x Installable