Yes, it should be hyperthreading capable. The problem with that, however, is if Dell disabled it they probably did not even include turning it on as an option. But check the BIOS at startup there may be an option to enable it.
I have this problem with my Prescott on a Dell XPS. It's capable of a BIOS update to enable 64 bit instructions, but Dell never included it as a BIOS update for my motherboard.