32

Why is it that I see an A: drive and a C: drive but not a B: drive?

Is there a reason why the disk partitions start at C? And is it possible to change that letter designation?

random
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cdb
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9 Answers9

64

Because back in the day of floppy disks, there were either two physical floppy drives (A: and B:), or just one physical floppy drive (A:) with one emulated (B:) so you could copy from disk to disk by exchanging disks every few hundred KB.

Andrew Arnott
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9

The A and B slots are very useful when you want to give a particular removable device the same drive letter each time it's inserted. Windows will never assign A or B to a device, but if you assign A or B to a device using Disk Manager, that drive letter will be assigned on future inserts.

I keep my source control database on a USB key so I can transfer it between multiple machines, and always assign it to B because I know that drive letter will be available on every machine. Finding this trick simplified my life greatly.

Roger
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2

Can we change it ?

Sort of. Some RAM disk drivers and USB tools allow to assign the long lost drive letter B:.

Peter Mortensen
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1

You can map a drive as B: if you want. Under computer management, go to storage/disk management. Right click the drive you want and choose "change drive letter/paths" You should be able to select B: as an option.

takanara
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0

Disk Manager (part of Computer Manager) will allow you to assign 'B' to one of your drives.

Peter Mortensen
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uSlackr
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0

I use the B drive for mapping network drives when I've run out of other letters (surprisingly easy to do with USB hubs and such).

Rich Seller
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My Windows XP box at the office has no C drive either. There was a bug in the text-mode setup version I installed from that was triggered by having a Zip drive (think 100 MB floppy) installed when running setup, resulting in Windows XP installed on drive E.

I've found it entertaining (and even occasionally handy) to have no C drive. Quite a few application installers have shown "quirks" when faced with no drive C at all.

Peter Mortensen
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RBerteig
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0

I've seen Softgrid (now called Microsoft Application Virtualization (App-V) version 4.5) installs which use the B drive as it's hidden drive... It uses the drive to store the applications to run.

Here is how to do that: http://social.technet.microsoft.com/Forums/en-US/appvbeta/thread/d9d46885-d136-4ace-9cd9-3b881322b86a

jeah subst isn't a good idea but if you are on XP or older and need to change the drive letter to B: then go to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices and change \DosDevices\Q: to \DosDevices\B:.

Davy Landman
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-3

A: is for 3.5 floppy drives, B: was for 5.25 drives, noone uses 5.25 anymore so B: is no longer assigned.

acme64
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