Numbers of processor in core 2 duo system

2 cores without hyperthreading. 4 virtual cores with. but still only 2 actual real cores as they can split threaded workload (progrom instructions) to run 2 instructions at the same time giving the illusion of another core.
in task manager a core 2 duo with hyperthreading will show up as 4 cores turn it off in bios and you will be back to 2.