Quote Originally Posted by doc_bean
Err..doesn't defragging damage the HD (ever so slightly) ?
I recall, from a years back article, that a low level format is damaging for HD performance by removing 'markers'. It was required for some sort of rescue, forgot what, but also removed 'markers' (?) on the HD which were there for normal smooth operation.

As the defrag proces basically moves data from one block to another, I can see files getting damaged due to copy errors.

A defrag tool that is incompatible with your OS version and/or filesystem will corrupt your system.