OK - I picked up a Poweredge 840 for personal use (home lab, directory, sandbox, etc...).  This was originally a Pentium D host but has been upgraded to a 3000 series Xeon (SL96E / 5030).  According to Intel ( http://www.intel.com/Assets/en_US/PDF/specupdate/313065.pdf  and http://ark.intel.com/products/27208/Intel-Xeon-Processor-5030-(4M-Cache-2_66-GHz-667-MHz-FSB) ) this processor supports virtualization. I am running Centos 6.2 and the host OS is up and stable.  Virtualbox is installed and will allow the creation of a baseline VM - but when launching the VM I get the following error message:

Failed to open a session for the virtual machine Home-DC.
VT-x is not available. (VERR_VMX_NO_VMX).

I've been digging through the forums here and elsewhere and have found some good information indicating that virtualization on the PowerEdge 840 is possible - but I have not been able to get this working.  

Dell documentation states that the 840 with Xeon processors support this functionality (page 12 of http://support.dell.com/support/edocs/software/HyperV/en/sov/sova00.pdf )  

The common thread that I find as I research is that I need to turn on hardware virtuialization in the system BIOS.  In short - I have looked through every single configurable item in bios and I don't find any reference to this.   BIOS was A01 when I got the machine - has been updated to A08.  I have rebooted a number of times, validated that A08 is in place, but I never find this option.

In this thread: http://en.community.dell.com/support-forums/servers/f/956/t/19438390.aspx  I find a user with a very similar configuration who sees success after rebuilding the machine.  I am trying very hard to avoid a rebuild.  

Any thoughts?