To be honest, it is difficult to know whether the board supports virtualisation or not.
I know for sure that most of the Intel Desktop Board 'Q' Series (like dq45cb, dq45ek, dq965gf, dq35jo, dq43ap etc.) has the virtualisation options in the bios, reason being that these are Vpro capable machine, and one of the Vpro requirement logo certification is to have a board that supports VT-d.
I have checked on the release notes of the bios for the Intel ® board DG43NB:
It says that one of the new fixes is that "Removed VT-d option from BIOS setup menu."
Now regarding the CPU:
you can check it on the link below, get the CPU SL number and check it manually.:
For CPU Q8400, it does support VT.
For CPU Q8400S, it does support VT.
Hope this helps a bit. When in doubt, check with the Intel® Customer Support.
All the best,