Try this, very easy to do and costs nothing.
If you suspect it's HD related, physically remove the power chord going into the back of the PC. This severs any connection that may be present in ground. I've used this numerous times and has corrected problems with PC's and electronics as well.
If condition persists, open up your PC case and touch the case with your hands to eliminate any possibility of static electricity shorting out any circuitry. Make sure you have a good solid connection from both of your IDE cables to the motherboard and whatever drives you have installed. Next check the memory sticks are not loose and properly seated.
Hope this helps.