Mbunny & Vsync: -
I can remember struggling like this many years ago with power supply designs. Thermal paste (heat sink compound) to most computer assembly buffs or low-voltage aficionados forms part of the tools of the trade, if you have the necessary training and knowledge. Can you buy it at you local store? Do motherboard/CPU retailers stock it? It’s been my experience that even at large retail computer outlets in the UK most have never heard of it, including so called in-house help and support personnel. I’ve had a recent bout with so called technical support personnel where the store security officer actually new more that the in-house professionals.
Ok modern CPU heat sinks come with the (mandatory) plastic pad that has the compound in place, but what happens if it’s a return to the store, do they re-apply the compound? Don’t think so; and as this type of sink has to be orientated correctly (in both planes) or the plastic pad will be connect to the CPU and not the metal, applying compound will not help either as there will be a small gap between the CPU and heat sink.
Just for the sake of clarity, this may not be the problem, but I suspect it’s a contributory factor.
Young or new people to this game require our help and support if possible, what took me twenty or more years to learn by training and tria-and-error can be learned here in a week (well nearly).
Keep helping.