Helping people with computers... one answer at a time.
Whoa ... seems my answers around the I386 direectory have been generating lots of additional questions as well. Let's see if we can clarify they "I386 mystery".
Let me start by answering a question you didn't ask, because it's related, incredibly important, and the reason that I386 appears in so many of my answers: In my opinion, you should never purchase a pre-installed operating system without also getting the CD-ROM of the operating system that came pre-installed.
Clear enough? Now, let me tell you why I feel so strongly, and how it relates to I386.
If your machine has a "C:\I386" directory that contains several thousand files, and that directory takes up over 600 megabytes of disk space then that is the directory I'm talking about. It is most likely a copy of the Windows XP Installation CD-ROM, or the I386 directory that is on that CD-ROM. If you find an I386 directory elsewhere ... say as a subdirectory buried somewhere else on your system, then that is not what I'm discussing here.
Note that I said it's just a copy of the installation CD-ROM. It's not created or installed automatically, it's a copy of the original installation CD-ROM made by whomever set up your machine, usually for two reasons:
Those two are related.
As an example, when you add hardware to Windows - say you add a new printer - Windows needs to get the appropriate files to support that new device. Since it wasn't connected to your computer when you set up Windows, those files were not installed then; they need to be added now. Where do they come from? The Windows Installation CD-ROM.
But what if you didn't get a CD-ROM when you purchased your computer? By having a copy of an installation CD-ROM in the C:\I386 directory, when Windows asks for the original CD, you can tell it to look there instead. So even though the manufacturer didn't give you a physical CD-ROM, everything you need is already on your hard disk, right there in C:\I386. When Windows needs something from the original install CD, it can locate it there instead.
Can you see the flaw in this setup?
What happens if your hard disk crashes? What happens if you need to reformat your hard disk? Everything is erased - including C:\I386. If you don't have an actual, physical, CD-ROM to reinstall from, you're screwed - to put it mildly.
The second reason for C:\I386 existing is simple convenience. Even if you have the CD-ROM, as you should, it's often more convenient to keep a copy on your hard drive. That way, instead of reaching for the CD-ROM each time Windows needs something, you can just tell Windows to pick it up from C:\I386, already on your hard disk. In fact, it's such a convenience, and disk space is so plentiful these days that copying the Windows XP CD-ROM to my hard disk is often one of the first steps I take when I'm about to set up a new machine.
So what does all this mean? Well, remember that C:\I386 is just a copy of a Windows Installation CD-ROM. Hence:
C:\I386 is not required for Windows to function. You can certainly copy it elsewhere, perhaps to a different drive, or back it up to CD-ROM or DVD. (Even though it's a copy of a CD-ROM, some manufacturer's appear to add to it, so that the actual C:\I386 will no longer actually fit on a single CD-ROM).
But it is convenient.