I purchased a Western Digital 500GB external "My Book" Hard Drive to use primarily as a back-up. I bought it in August, 2007. In mid November, the drive suddenly became unusable -- my computer no longer recognized it. No warning. changed the cable went through all the investigations to determine that all was lost. Data recovery was estimated to be from $500 up to $2, 500 -- making this the most expensive -- and the least reliable --hard drive on the market today!!!