For M1 HD overheating, I took the 'cheap' way out... I drilled 1/4" holes in the top cover above the power supply (6) and over the CPU (2-3), and 2 more below the power supply area, which already has lots of venting. Then I set it so there is extra space below it for ventilation, instead of setting it directly on a flat surface. Later, I may mount taller spacers to the bottom, instead of sitting it on matchboxes. This has been working good for me, even running it 24/7. It does occasionally go off, but now it is rare, like once every 2-3 weeks. I think this is not too bad for using it 24/7 to feed a modulator for in-home distribution.