First of all let me inform you that this community is solely dedicated to Intel vPro technology so for a motherboard or CPU related problems, in future kindly post your problems in our Processors or Motherboards communities respectively to receive a prompt response.
Now getting back to your problem, Q8400 is VT enabled and supports Virtualization of course. As for DQ45CB, it is compliant with Q8400 but in Q8400 we have two SKUs and DQ45CB supports http://processorfinder.intel.com/Details.aspx?sSpec=SLGT6 so be sure that if you order DQ45CB with Q8400, you are getting Q8400 with sSpec #: SLGT6 in order to avoid any incompliance issues in future.
Furthermore, if you plan to run ESXi/ESX 3.5, this platform should run it because of VT however for VMWare, we recommend use of Server boards & Intel Xeon processors. Running ESXi/ESX 3.5 is at your own risk or you might would want to check with VMWare team beforehand just to be sure.
Hope this answers your question, thank you and best of luck!
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