Hardware Virtualization on a OptiPlex 755

I have a fresh batch of OptiPlex 755 systems that just arrived. When trying to install my VM clients (Virtual PC 2007, VMWare Server 1.0.4, etc.) I've discovered that these systems/models do not appear to have any hardware virtualization available to my virtual machine clients. I have gone into the BIOS and enabled the option under the "Performance" => "VT for Direct I/O". On a OptiPlex 745 it was just listed as "Hardware Virtualization" not "VT for Direct I/O", and likewise the option doesn't appear to have worked like the VT option on the OptiPlex 745s.

Within Virtual PC 2007, under "Options" => "Hardware Virtualization" it is reporting "Note: Hardware-assisted virtualization is not available on this computer."

The current configuration is:

OptiPlex 755 - BIOS A03
Intel Core 2 Duo - Processor 4400 (2.00GHz)
Windows XP Pro w/SP2
2.0 GB RAM

...any ideas? I thought this processor supported Hardware VT. The description in the BIOS for "VT for Direct I/O" is as follows (which makes me assume VT SHOULD be available):

"This field specifies whether a Virtual Machine Monitor (VMM) can utilize the additional hardware capabilities provided by Intel(R) Virtualization Technology for Direct I/O"

Thanks
-Rob Haas