I want to replace the mains lead on my nokia ondigital box with a better quality one.This should prove quite straight forward but I've hit a stumbling block. I can't get into the case! Most of the screws are normal torx headed ones but the ones on the sides are torx but with a raised centre pin ( probably some sort of security measuree). Does anyone know what sort of fastener this is and if I can get a suitable driver for them??