This gt 210 is really quite old and is passively cooled-i just wanted to experiment with it in order to familiarize myself with the procedure of changing gpu thermal paste which is something i had never done before.
IMO, go to any shop that repairs TVs, radio, amplifiers, sells remote hi remote and rca cables. They use thermal paste frequently on mosfets and linear regulators. A small syringe of thermal paste costs 10 rupees only whereas 30 grams boxes costs 30 rupees easily and would be enough for 50 processors. It would still be cheaper then amazon if I buy thermal paste and parcel it to you.
Just go to nearest electrical shop and buy it for much less price.
Put a very small drop (2mm x 2mm) of thermal paste in center of the GPU die, it will cover the whole processor when you place the heatsink over it.
Plonk the GPU in PC and stress it suing furmark and check the temperatures = should be normal no matter what.
If temp. is still not normal then take it out, remove the heatsink carefully and see gpu die if its actually fully covered with the paste. If not, clean the old paste, apply new paste again with more care while improving your mistakes, put the heatsink back, plonk the gpu, stress it and check it.
It temp. is still not good, then consider your GPU to be old and with the time they can adapt a tendency to run hotter with old capacitors and inductors. Buy a small fan from the same shop for ~30 ruppes, fix it with jugaadh on gpu and use it.
AT the end of the day, you need to cool the gpu.
The system now idles at around 44 C but upon load (such as while playing high bitrate 1080p videos at 50-60% cpu utilization), the temps go upto 68-73 c.
Being the same 775 socket but twice the faster then your c2d, If your C2Q is bit hotter then I feel it's okay.
Sir.
Again, as described above, all you can do is
VISUALLY INSPECT if the processor is fully covered with the thermal paste or not OR if the 775 heatsink with plastic legs fully inserted in holes and fastened or not.
Remove your heatsink, see if thermal paste you applied there was enough or less (should be enough in most cases, thers hardly any space ebtween heatsink and processor). Remove old paste, clean the processor surface, apply new paste in a drop or X format, put the heatsink back, make sure all the clips are properly fastened inside their holes, boot the pc, throught a stress test.
If still temperature underfull stress floats around ~65 then its okay.
You actually can't do much with old gt210 and Core 2 chips. Only you can provide them are basic resources like power, air and thermal paste.