Back in the day, floppy disks were a: and if you were lucky b:, then when permanent storage came along c: was the default for hard disks (as I remember it)

Now that many computers no longer have floppy disks is it possible to have your primary hard disk as A: is the convention out dated?

Removable drives (like DVDs and flash readers) now seem to take lower precedence than permanent storage so it is a bit of an oddity that floppy disks should have earlier letters.


Your computer can use up to 26 drive letters, from A through Z. Use drive letters C through Z for hard disk drives. Drive letters A and B are reserved for floppy disk drives. However, if your computer does not have a floppy disk drive, you can assign these letters to removable drives.

From the allknowing Microsoft Knowledge Base

Before you modify drive-letter assignments, note the following items:

  • Changing the drive letter of the system volume or the boot volume is not a built-in feature of the Disk Management snap-in.
  • Many MS-DOS-based and Microsoft Windows-based programs refer to specific drive letters for environmental or other variables. If you modify the drive letter, these programs may not function correctly.

How to remove a drive letter

To remove an existing drive letter on a drive, on a partition, or on a volume, follow these steps:

  • Log on as Administrator or as a member of the Administrators group.
  • Click Start, click Control Panel, and then click Performance and Maintenance.
  • Click Administrative Tools, double-click Computer Management, and then click Disk Management in the left pane.
  • Right-click the drive, the partition, the logical drive, or the volume that you want to assign a drive letter to, and then click Change Drive Letter and Paths.
  • Click Remove.
  • Click Yes when you are prompted to confirm the removal.
  • The drive letter is removed from the drive, from the partition, or from the volume that you specified.
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  • I didn't know you could assign a: and b: to other removable drives, thanks. – Jeremy French Jul 30 '09 at 14:39
  • Although I do have a floppy disk drive A, but Windows Disk Management won't let me change my CD-ROM drive letter to B even though is unassigned. – martineau Mar 13 '11 at 17:12

Yes, you should keep your primary hard disk as C:, because there's still a lot of software that has paths hard-coded into it in one way or another. Alternate drive letters for the primary hard disk is something that almost no one tests for, and so you'll end up finding subtle breakage in lots of places.

I'm not saying that you shouldn't be able to do it (heck, Windows works just fine if you install to a primary other than C:), but you don't have a Windows computer just to run Windows, you'll want to put on other software. And there's plenty of companies out there that can't get it through their heads that they need to use the variables, not hard code paths.

So, if you want a 'it just works' experience, keep your primary hard disk as C:, and have Windows installed in the default location.

You can survive doing it otherwise, but you'll regularly run into annoying problems.

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You would be amazed at how many freshly developed, "cutting edge" applications assume c:\ to be the primary hard disk.

The convention may be outdated but guys who write the apps are still pretty "dated" for lack of a better word :)

My recommendation? Keep the C:\

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Trying to build a consensus answer here, please vote or edit as you see appropriate.

While the idea of drive letters is becoming deprecated, keeping a hard drive available on drive c: is still a good idea. A lot of software still assumes that drive c:\ is present and persistent.

It may be an archaic standard but drives A: and B: are reserved for removable disks. Other than drive C: there is no guarantee that a drive letter will be present, permanent or writable.

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To a certain extent the whole concept of drive letters is redundant. O/S such as Home Server from Microsoft simply aggregate the available disk space together and use raid-like techniques to ensure that if any physical device fails you won't lose any data.

I'd say the primary reason we're stuck with it in Windows is that Microsoft doesn't want to break all the software that is written to expect things this way. However it wouldn't be too difficult to provide the software with a virtual drive letter and simply treat the separate drives like one. The only tricky thing there would be installing the new O/S on drives with existing data.


Considering XP was around when floppy's were the thing, it is still the mainstream OS even though it is around 8-9 years old. So I guess I'm not that surprised that A and B are still skipped.

I remember someone at high school saying that they installed their windows instance on D: instead of C: so he couldn't get attacked or get viruses. I didn't have the heart to tell him about windows system variables (like windir and systemdrive). =)

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I think it falls under the "if it ain't broke...". I don't see any real advantage to changing the conventions and it would break a few old (some would say obsolete) assumptions. Pretty much a non-issue all the way around...

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As best I can tell, the drive letters A & B have been reserved for backwards compatibility. Even though A: and B: are not in use, disk manager will not let you select either of those drive letters for your main boot partition. But I do agree with your point. A and B are no longer used so perhaps it is time for those folks at MS to jiggle the handle so to speak.

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    I have never seen a drive named B, does that mean I am not qualified to be a super user? :) – swamplord Jul 30 '09 at 13:02
  • nah, it just means you're too young to remember floppy disks that actually deserved the name! :) – Molly7244 Aug 23 '09 at 3:41
  • The last time I saw a B: drive was on my cousin's 286. He added one of those new-fangled 3.5" floppy drives! – Anthony Giorgio Sep 11 '09 at 21:53

I configured and ran a machine on Windows XP with the boot drive being K. It ran fine for many, many years before eventually being scrapped when the motherboard quit. It was done this way because the early days of SATA ports required drivers from floppy and by the time that was all loaded up, the boot drive had assigned itself to K and I was unable to change it.

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