To be truthfull, I quite like it when people try defragging drives on older machines, because often the extra extended workout will push any older tired drives (i.e. anything over three years old) over the edge. By defragging an older drive you run a very high chance of killing it
I have to ask - why do you like this? Do you also enjoy watching peoples houses fall down? Bizarre I have to say.
By the way I regularly defrag drives and have yet to have any hard drive fail in any way whatsoever. Maybe I have just been lucky over the last 25 or so years.