Q Almost everything that I read says that a low-level format on a hard drive should only be done at the factory. If this is true, then why does a modern BIOS have such a feature?

A To format an IDE drive from scratch involves three steps:

1. A low-level format to create the sectors on the drive. This is done at the factory and is specific to a drive. When you purchase a drive this will already have been done for you.

2. Partitioning the drive. This is common to all IDE drives and is done with programs such as Fdisk or PartitionMagic.

3. A high-level format for the operating system. Examples of high-level formats are FAT16 for DOS and Windows, FAT32 for Win 95 OSR2.x and Win 98, NTFS for Windows NT, and HPFS for OS/2.

The need to perform a low-level reformat on a drive rarely arises. However, according to one hard drive manufacturer, a low-level format may be necessary in three situations:

1. The drive has been infected by a virus which cannot be removed unless the boot sector is destroyed.

2. Increasing numbers of bad sectors are appearing on the drive.

3. You are switching permanently from one operating system to another and want to remove all data from the drive.

If you choose to proceed with a low-level format, the best solution is to obtain a program from the manufacturer for your model drive. This software creates the sectors and positions them on the drive for optimal performance. If you donÆt use software designed for the drive the result could be poor performance or even a drive that no longer works.

However, just to confuse matters, many programs that say they do low-level formats actually don't. On larger drives, manufacturers vary the number of sectors per track. However the IDE controller cannot deal with different numbers of sectors per track. They then use circuitry on the drive to translate the sectors so that the physical and logical sectors differ. In this circumstance the low-level format cannot change the location of the sectors and so is not a true low-level format. But it will completely clear and rewrite the information in the sectors in their current locations as a true low-level format would.

It should be noted that the same software will rearrange the sectors on a drive that does not use sector translation.