Wow... Very impressive post. Not sure I can add much that you don't already know.
First thing I found was an article about Power Spikes in your home/office and how it can cause HD Clicking/Failure.
Also, this quote from Tech Support Forum:
"...So far. I am wondering if people who are having these issues are using rounded IDE cables? I have a funny idea that it is a control related issue.............Not sure why there should be any difference but I have noticed this occur only when I changed to rounded cables. I have a funny feeling if you took this drive to another PC - say a P4 with a fairly good MB and standard IDE 133 cable, there would be no clicking.
The clicking? More of a power down then power up noise with the head arm seeking furiously. If you are using XP or 2000 with the drive set to Dynamic, then you have some issues if you can not read the data on your PC...."
Wish I could help more. brad