Strange problem with intel e2160

I am facing a vary strange problem with the processor(I have already frustrated intel and microsoft technicians with this)

Task manager and device manger display one core sometimes and when I restart the pc, one either appears or disappears i.e. two cores are working at some time and both the cores are working at some other. This happens quite randomly.

I sent the motherboard for warranty replacement through my computer engineer but somehow i feel it is the same. Anyways, the motherboard is out of warranty now

So what could be the problem. The Intel Proc Id utility also show one core 'disabled' at times when ony one is working

Any suggestion???

Open Task Manager
Click on View > CPU History > One graph per CPU

If that is already enabled you may have a conflict with CPU driver (automatically installed by Windows)
Therefore, run Bios setup defaults and re-install Windows clean

Tried reinstalling the OS(win xp)

Also tried installing win7 rc but the same issue is there

Any inputs??

Check voltages for both cores. speedfan can do this.

Please see the attachments