Are you sure your processor supports Intel Virtualization (VT-x) or AMD Virtualization (AMD-V)?
Here you can find Hardware-Assisted Virtualization Detection Tool ( http://www.microsoft.com/downloads/en/details.aspx?FamilyID=0ee2a17f-8538-4619-8d1c-05d27e11adb2&displaylang=en) which will tell you if your hardware supports VT-x.
Alternatively you can find your processor here: http://ark.intel.com/Default.aspx. All AMD processors since 2006 supports Virtualization.