Vista - reformat hd

Question: When reformatting hard drive using the recovery disc's, how many times is the hard drive being rewritten? Just curious, plus the question was put to me and I had no answer. Thanks.

I dont think it is being re-written at all. It is only "re-written" when the O/S re-installs and/or data written back onto the drive.
When you format a disk, the operating system only "zeros" the root directory and the tables containing the list of sectors on disk that are occupied by files. Pay attention when you format a hard drive, a message "Verifying x%" is shown. The hard drive isn't being formated; the format command is only testing the hard disk magnetical surface in order to see if there is any error and, in case if a error is found, mark the defective area as bad (the famouse "bad blocks" or "bad sectors").

That is why recovery software is able to retrieve the HDD data on those areas of a "formatted" drive not overwritten by the newly installed O/S or newly installed programs/data.

Essentially "formating" is akin to removing the "table of contents"-the directory of the HDD contents. i.e., like taking a book and ripping out the "table of contents" page. The data is still on the drive, just as the pages are still in the book- untill it is written over again, and If you know how to reconstruct the "table of Contents" on a HDD, much of the data is retrievable.

There are programs that write symbols/numbers/giberish over the entire drive repeatedly-this is the only way to truly "overwrite", or format data on a drive. The best way to make the data on a HDD "unrecoverable" is to destroy the drive itself.