The story I heard was more about older style 5 1/4 drives. We called them ''Winchesters''. With these you did low and high level formatting during which you adjusted the "interleave" factor which was the number of disk rotations between read/write operations which allowed time for the heads to move into proper position. 1 to 3 interleaving was common with early drives. These were heavier units and the logic was that gravity had an affect on components...especially the heads. It was said that these could sag and tracking could change when turned 90 degrees. Thus, with these drives, you compensated by performing low and high level formatting in the position the drive would be running. With IDE drives, you no longer low level format at end user level and I have heard/read that changing the orientation of the drive is not the issue it once was. However, I still format a drive after installing it permanently just as a habit.