kat -

When you have more than one physical hard drive, or when you make more than one partition on a single physical drive, they're labelled using alphabetical "names." In Windows, or in DOS where the system came from, the A:\ and B:\ names are reserved for "removable media" drives which are usually floppy disk drives.

The first Hard Drive is nearly always called the C:\ drive. If you add additional hard drives, or additional partitions on the one you have, they're named in sequence as your D:\, E:\, etc. proceding up through the alphabet.

A "tradition," more than anything, usually makes the first "Optical Drive," a CD pr DVD reader or burner, the E:\ drive, and the next "Optical Drive" the F:\. If you have two hard drives, or two partitions on a single hard drive, the first one is nearly always C:\ and usually the second one is D:\. Even if you don't have CD or DVD drives to occupy the E:\ and F:\ positions in the list, sometimes a new hard drive that you add will skip to G:\ to continue the naming, but this isn't a strictly observed convention.

As an example, my computer came with:

a floppy drive A:\,
a 120GB internal hard drive C:\,
a 250MB ZIP drive that was treated as a "hard drive" D:\,
a DVD/CD read-only drive E:\,
a DVD/CD burner F:\.

When I added an external USB hard drive, it automatically took the "name" G:\.
Because I didn't "clean up" when the external USB failed, the replacement external drive that I use regularly is H:\.
When I plug my digital camera in it becomes the I:\ drive,

and when I plug my "reserve" 160GB external USB hard drive in for backups it's the J:\ drive.

Again more out of tradition than anything, when you connect to "drives" on a separate machine via a network, the customary name assignemnts start with Z:\ and work backwards through Y:\, X:\ etc. It's fairly common for system administrators to change the default so that when you "map" a network "drive" that you're permitted to access it appears as either Q:\ or R:\ and acts (mostly) just as if someone had installed a new separate hard drive in your own machine.

In traditional language, the A:\, B:\, C:\, ... X:\, Y:\, Z:\ refer to the different "physical spaces" where you can read or write the files that you use. Since any separate partitions on a single drive each "looks like" a separate physical device to the operating system, Microsoft "deprecates" even calling them "drives." The current preferred use is to call them "Volume A:\," Volume B:\," etc.

For most PC users, C:\ just means "where you put everything" or "where you put the Operating System and Programs." If it's the second choice, you usually have a D:\ that's "where you put data," or your D:\ space may be "where you keep archives or backups."

The way you use a separate "Drive" (or using Mickey's terminology, a separate "Volume") is entirely your choice. In the case of separate physical devices it's a bit like having two separate file cabinets to keep things in. In the case of two separate partitions on the same physical drive, it's perhaps more akin to having separate drawers in the same file cabinet.

The alphabetical names for your drives are mostly a tradition, although it's a fairly well embedded tradition. If you wish, you can change the "alphabetical name" for any drive to a different letter reasonably easily with most recent Win versions. ("Reasonably easily" may be questioned by some who've tried it.) You can also choose to have Windows Explorer show a "display name" of your own choosing, so my 7 "drives" could show in Win Explorer as Clyde, Zelma, Herbert, Dweeb, Oscar, Sweetie, and Sourpuss.

With WinXP, and with some earlier versions, it's even possible to "join" two or more physically separated "drives" into a single "volume" that looks, to you and to any programs that run on your machine, as if you had one single larger drive. This is akin to having several file cabinets and a secretary. You don't know, and don't really care, which file cabinet your secretary puts stuff in, as long as your secretary can bring it back when you ask for it.

Whether it's a separate drive, or a separate partition, having too much "stuff" on one is just like having a file drawer that's jammed so full that you can't easily sort through it to find the letter (file) you wan't. You'd probably pull out a few folders and lay them aside until you finished looking, and then you'd jam them back in where they belong. With files on your computer, you can't just lay the folders you pulled out on top of the file cabinet, you have to put them in another drawer (move them to another drive). When you've found what you're looking for, or "corrected the sorting because the dumbass boss messed it up when he got in your file drawer" (finished the defrag), you move the folders from the drawer (drive) where you put them temporarily, back to where they belong.

A backup or archive drive probably won't get fragmented too rapidly, so not bothering is probably okay if the files/folders on the drive aren't changed frequently.

Since Windows programs always makes a temp copy of any file that is opened, and the temp nearly always is made in the same folder with the original file, if you get really jammed up and there isn't enough space where the original file "lives" to make the temp copy, it's remotely possible to get a situation where you can't open a perfectly good file, although you still would probably be able to copy it somewhere else where it will run. Usually something else breaks before this condition is reached.

Especially with NTFS format, with WinXP file management, a desktop drive doesn't really need to be defragged very often. The main reason for doing it regularly is that the more fragmented it is the longer it take to defrag, so if you let it go too long it may take a somewhat longer time when you do get around to it. The less free space you have on a drive, the more benefit you get from more frequent defrag.

Defrag is needed more frequently on laptops simply because laptop hard drives typically are about one-tenth as fast as modern desktop drives, so having everything in optimum condition often does have an effect on operating speed.

Defrag is a critical need with some older Windows versions because most of them can only write operating system temp files withing a single contiguous space, so if the free space gets fragmented and there isn't a large enough single empty space for the temp files that the system needs, it may slow drastically or may simply stop. WinXP can splatter most of the temp files it uses just about anywhere, so it's much less critical.

John