My power supply has just started to make ominous grinding noises, so it
looks like I'll want to whip out the fan and replace it before the thing
melts on me. However, I have to admit that I'm terrified of opening the it,
as I gather you can get quite a nasty (potentially fatal) shock if you don't
know what you're doing.

What precautions should I take before opening it up? Please err on the side
of paranoia in your advice; I only need to do this once and I *really* don't
want to go to hospital over it :-)

Ewan