The best way to understand how partitioning works is by viewing partitions graphically. Posted here is a screen-shot taken from Partition Magic. Here you see 6 hard drives. [Actually, you can't see all of Disk #6.] The first 3 disks are SCSI. The last 3 are IDE/ATA. The legend for this graph is posted here.

Notice that Disk #3 contains both NTFS and FAT32 partitions. Notice, too, how multiple logical DOS drives are always enclosed with-in extended partitions [light-blue outline].

If you look closely, you can see that Disk #6 has no primary partitions. This disk is comprised entirely of an extended partition, containing multiple Logical DOS drives.

This is a trick you can use when adding a new hard drive to your system. If you partition a newly added hard drive so it contains no primary partitions (only Logical DOS drives within an Extended partition) ..

.. it will prevent the newly added disk(s) from usurping drive letters from Logical DOS drives already installed in your system. [Because Windows assigns drive letters to all primary partitions before it does to any Logical DOS drives.]

Two Common Problems

1. Not using the entire amount of the disk. For example, after partitioning your 120-GB drive into 3 equal parts [you thought], you find you're only using 80 gigs. To avoid this problem:

When creating the Extended partition, ensure you use the *entire* amount/size of whatever is left after creating the Primary partition.
Continue to create Logical DOS drives until *all* the space is used. [Obviously, if you only make one, large primary partition, neither of these items apply.]

2. After partitioning, you later discover one of the partitions didn't "take" [for whatever reason]. As a result, you end up formatting the wrong drive, and losing valuable data. Obviously this is bad, bad, bad. To avoid this problem:

After partitioning, do not immediately format the new partition(s). Instead, reboot and return to FDISK. From there, select your new disk and view the partition information to verify they "took" [Select item #4: Display partition information]. Ensure the partitions and drive letters look the way you expect them to.

I have had to re-do partitions before, because they didn't 'take' the first time. Simply repeat the process. Format only after you are positive that all partitions you created (thought you created) look the way you expect them to.

Drive Letters

Windows assigns drive letters like so:

1st -> Primary partition of Primary-master
Next -> Primary partition of Primary-slave
Next -> Primary partition of Secondary-master
Next -> Primary partition of Secondary-slave
Next -> Primary partition on SCSI ID 0
Next -> Primary partition on SCSI ID 1 (and so on, until all Primary partitions for all SCSI IDs are assigned)
Next -> All Logical DOS drives of partitions on Primary-master
Next -> All Logical DOS drives of partitions on Primary-slave
Next -> All Logical DOS drives of partitions on Secondary-master
Next -> All Logical DOS drives of partitions on Secondary-slave
Next -> All Logical DOS drives of partitions on SCSI ID 0
Next -> All Logical DOS drives of partitions on SCSI ID 1 (and so on, until all drive letters are assigned to all Logical DOS drives on all SCSI IDs).

The thing to note here is that *all* Primary partitions receive drive letters before ANY Logical DOS drives do.

Pay particular attention to the drive letters FDISK assigns to these new partitions. You will need this information when it comes time to format these newly created partitions [in the next step]. If you format the wrong partitions, you're screwed.

You will lose all data in the partitions you format. [In the section labeled Data Recovery below, you will find a list of programs that might help if you accidentally partition or format the wrong drive.] Write down this drive-letter information on a piece of paper.

Another method to avoid formatting the wrong drive is to use descriptive drive labels. At the completion of formatting, the program will ask you if you want to label the drive. If you don't, it will automatically assign some arbitrary, meaningless label for you. It's better to label each partition yourself. Use something that makes sense to you, such as: C_drive, or D_drive, etc.

Letter-based labels can become confusing if/when you add more hard drives. Your F_drive, for example, might become your G_drive or H_drive when you add another hard drive later. But you can always change their label. I tape a 3x5 card to the side of my monitor. It contains all partitioning info, in a single glance.

A third trick to keep from formatting the wrong drive is to make all your partitions unique sizes. For example, if you have two 60-GB drives, instead of creating three 20-GB partitions on each drive, you might make one drive: 15-GB, 20-GB & 25-GB, and the other 12-GB, 18-GB & 30-GB.

This would make it difficult to confuse your partitions, and easy to tell them apart. If you need to reformat a particular drive, and that drive is supposed to be 18-GB, but it's being reported as 25-GB, you know something isn't right.

Lastly, you should *always* have a back-up image of your boot partition(s) on hand. You can create a back-up image with an imaging utility such as Symantec's Norton Ghost, or Powerquest's Drive Image. If you need help with creating an image of your boot drive/partition, check out the world-famous Radified Guide to Norton Ghost.

This way, if you ever accidentally wipe out [re-format] your boot partition, you can quickly & easily restore it .. in a matter of minutes. You shouldn't be without an imaging utility. They can save you from so much grief.

One of the tools that comes with Partition Magic, called DriveMapper, can help in the event the installation of a new hard drive causes drive letters to change on existing drives/partitions. From the Partition Magic Help file:

Drive letters can change when you create, delete, hide, or unhide partitions, which can cause applications not to run because application shortcuts, initialization files, and registry entries refer to incorrect drives. DriveMapper is a wizard that lets you easily update drive letter references.

If you are using Windows NT or Windows 2000 as your only operating system, we recommend using the Change Drive Letter operation (Operation Advanced Change Drive Letter) rather than DriveMapper. Change Drive Letter lets you permanently set the drive letters for your partitions so that adding and removing partitions does not affect drive letters.

If you install your OS to a SCSI drive, before installing any IDE drives, and make it your *active* partition, the primary partition on your SCSI drive becomes your C: drive. If you later add an IDE drive, your SCSI drive will remain your C_drive, even tho you have a primary partition on your primary-master drive. I have never done this, but this is what I've been told.

For more info about drive letter assignments, see here (annoyances.org). A freeware letter-assigner is posted here (I have not tried it). Ed K. from Topeka, Kansas writes to mention a free utility named COA (Change of Address). He says:

PCMag has a great little program that I've used many times under Windows W9x. It modifies registry entries, ini files, etc., so that, when adding a new drive letter, changes the system is updated with changes to previous drive letters. For example, you can tell COA to replace all D:\ with E:\ The program can be found at Hotfiles.com, search for COA. They also have a 32bit version available.

On the last page, we'll take a look at some final points, such as the advantages of NTFS over the FAT32 file system, formatting, data recovery, GDISK, and some other miscellaneous items.