But in fact it's an inappropriate analogy to compare this with a car engine and the distributor (not that modern cars have distributors any more, but still....).
The problem is this: the information on the (magnetic) hard drives is all stored in addressable sectors. As a simple analogy, think of it like thousands and thousands of little boxes, each with its own identifying number written on it (its "address"), and each of which contain small portions of information.
But only the central electronics of the hard drive (in the form of hardware, BIOS and OS) knows which information is stored in which "box". And to complicate matters much further, any particular string of information gets split up and placed into "boxes" all over the place - for example, a letter which says "Hello I am in Amsterdam, are you well?" might (simplistically put) have "Hello" put into Box 10342, "I" into box 71420, "am" into Box 63369, and so on. And only the central "brain" of the hard drive knows which of the boxes each of the words has been placed into, and in which order. Thus, if anyone wants to retrieve the letter, one needs the hard drive's "brain" to retrieve the parts of the letter in the right order from the right "boxes" (in this simplistic example, even a slight mistake from the "brain" might lead to the letter being incorrectly reassembled as "Hello, I am well, you are in Amsterdam".
So in a very real sense, if you fry the "brain" of the hard drive, it's immensely difficult - in many instances impossible in practice - to retrieve the data from the magnetic disc, even if the data itself is uncorrupted. All that you're left with, when you don't have the means to understand what is stored where, is an unintelligible cacophony of 1s and 0s, with no means of reassembling those 1s and 0s back into the correct, readable order.