Actually using the delete capabilities of the OS does nothing more than put an invalid charactor in the file tables that map out the HD. This lets the OS know that the disk space is free, but the data is still there until overwritten by something else. That's why Norton and the like can recover "deleted" files.

Formating the HD with the OS only prepares these file tables so the OS can write to the disk. It does not actually overwrite any data. You may not be able to access it through normal means, but until the data is overwritten, it's still there.

To change the geometry of the HD you need to use fdsk, Partition Magic (and the like) or the low level utilities that the HD manufacturer provides. Trust me ... you DON'T want to do a low level format on a drive larger than 2GB. The process will take over a week!!!