For clarification:
HLF (Last modified: Monday, December 02, 2002)
(n.) Short for high-level format, a formatting method that initializes portions of the hard disk and creates the file system structures on the disk, such as the master boot record and the file allocation tables.
High-level formatting is typically done to erase the hard disk and reinstall the operating system back onto the disk drive.
(v.) The process of performing high-level formatting
LLF (Last modified: Monday, December 02, 2002)
(n.) Short for low-level format, a formatting method that creates the tracks and sectors on a hard disk. Low-level formatting creates the physical format that dictates where data is stored on the disk.
Modern hard drives are low-level formatted at the factory for the life of the drive. A PC can not perform an LLF on a modern IDE/ATA or SCSI hard disk, and doing so would destroy the hard disk. Older MFM drives could be low-level formatted to extend the life of the disk, but modern hard drives no longer use MFM technology.
A low-level format is also called a physical format.
Floppy disks must also undergo low-level and high-level formatting, but these two are generally performed at the same time. On PCs, for example, the FORMAT command performs both a low-level and high-level format the first time a floppy is formatted.
(v.) The process of performing low-level formatting.
Unless you've done it on a 1, 2 gig drive (the max you can do it on, I think) or smaller, you haven't done a low level format as I understand it. As far as I know (which isn't saying much), erasing the partition tables is just another form of high level format. All the data is still there until overwritten. Just formating is also a high level format except that the partition tables are kept intact.
This article seems to back up my theory:
http://kb.indiana.edu/data/aaoa.html
These are hard drives that you can/cannot low level format:
http://kb.indiana.edu/data/adlt.html
Hard drive companies do LLF at the plant so they can bin their products (ie. a 60 gig has 15 gigs of bad sectors. They LLF it, "limit" the space it can hold, and sell it as a 40 gig) from what I understand.
Though, when I install I usually delete the partition table and format in DOS. However, I don't do that when dual (triple, quad,...etc.) if the other ones aren't buggered; I just fix that which needs fixin'.
That's how I understand it. Welcome to clarification and error correction, though.
***EDIT***
-definitions taken from webopedia