Tightening the screws quite well should probably feature in the drive upgrade faq, if it doesn't already.

We have had a couple of toasted units from this - mainly when the screw manages to short between the fuse casing and the side of the case... this is worst-case, as it bypasses the fuse and dumps rather a lot of current (when in-car, at least) through the PCB tracks, burning them out. It's *usually* fixable, though not very neatly and you end up with a big hole in the pcb that smells of burning

Hugo