Drive letter assignment rules

[Spoon2001]

Here are my current drive letter assignments (using Windows XP Home SP2)

C - IDE primary master hard drive, single partition
D - DVD+RW burner, secondary master
E - IDE secondary master, dock for removable drive trays, IDE hard drive
inside
G - currently unused - it is assigned to a 120G external USB hard drive
(single partition) when I plug it in, or to a 200G external USB hard drive
(single partition), when I plug either in
H - IDE primary slave, hard drive, single partition
F, I, J, K - assigned to flash memory card reader slots (CF, MMC/SD, Memory
stick, Smartmedia)
L - 1G USB thumb drive
M - 256MB USB thumb drive

Generally speaking, are these drive letter assignments persistent? They
seem to be. It seems that Windows must be storing some information about a
detected "drive", and if it detects that drive again, it assigns the same
drive letter to it if possible. But if it detects a new "drive", not
previously assigned a drive letter on this computer, it will assign it the
first drive letter that isn't being used, even if that letter has previously
been assigned to a different drive that isn't currently connected. Am I
right about this?

For example, XP assigns the same drive letter to a removable "drive" (e.g.
each flash memory card reader slots, or the CD-ROM drive) whether or not
there is any media currently in them (e.g. a flash memory card, or DVD or
CD).

Also, if I boot up without either external USB hard drive connected, the
drive letter G is not assigned to any of the other connected drives. Those
drives keep the same letters they had before.

However, it's interesting that Windows assigned the same G: letter to the
120G external USB drive or to the 200G external USB drive, whichever is
connected.

Ideally, I suppose, I would like for the same drive letter to be assigned to
the same removable drive. For example, if I am backing up files to a
particular USB thumb drive based on a drive letter, I want Windows always to
assign the same letter to the same thumb drive, so that the files will be
backed up to the intended thumb drive.

On the other hand, Windows did assign the same drive letter to two different
external USB hard drives? I just changed the assignment for one of these
drives. Now when I plug in the 200G drive, it is assigned letter G, and
when I plug in the 120G drive, it is assigned letter N.

Not surprisingly, when I plugged in my Drive N into a different computer, it
was assigned a different drive letter. Drive letter assignments are
specific to each computer.

Am I right about all this?

 

[Uwe Sieber]

Yes, your are right about all this. That two different USB drives
get letter G: is indeed very unusual. The only explanation is that
the drives enclosure have identical USB controllers with identical
USB serial numbers. In this case it is impossible to use them at
the same time. Is it?
http://www.uwe-sieber.de/usbtrouble_e.html#identical_drives

To get control over the letter assingments for USB drives I wrote
the USB drive letter manager:
http://www.uwe-sieber.de/usbdlm_e.html


Greetings from Germany

Uwe

 

[Jonny]

Here are my current drive letter assignments (using Windows XP Home SP2)

C - IDE primary master hard drive, single partition
D - DVD+RW burner, secondary master
E - IDE secondary master, dock for removable drive trays, IDE hard drive
inside
G - currently unused - it is assigned to a 120G external USB hard drive
(single partition) when I plug it in, or to a 200G external USB hard drive
(single partition), when I plug either in
H - IDE primary slave, hard drive, single partition
F, I, J, K - assigned to flash memory card reader slots (CF, MMC/SD,
Memory
stick, Smartmedia)
L - 1G USB thumb drive
M - 256MB USB thumb drive

Generally speaking, are these drive letter assignments persistent? They
seem to be. It seems that Windows must be storing some information about
a
detected "drive", and if it detects that drive again, it assigns the same
drive letter to it if possible. But if it detects a new "drive", not
previously assigned a drive letter on this computer, it will assign it the
first drive letter that isn't being used, even if that letter has
previously been assigned to a different drive that isn't currently
connected. Am I right about this?

For example, XP assigns the same drive letter to a removable "drive" (e.g.
each flash memory card reader slots, or the CD-ROM drive) whether or not
there is any media currently in them (e.g. a flash memory card, or DVD or
CD).

Also, if I boot up without either external USB hard drive connected, the
drive letter G is not assigned to any of the other connected drives.
Those drives keep the same letters they had before.

However, it's interesting that Windows assigned the same G: letter to the
120G external USB drive or to the 200G external USB drive, whichever is
connected.

Ideally, I suppose, I would like for the same drive letter to be assigned
to
the same removable drive. For example, if I am backing up files to a
particular USB thumb drive based on a drive letter, I want Windows always
to
assign the same letter to the same thumb drive, so that the files will be
backed up to the intended thumb drive.

On the other hand, Windows did assign the same drive letter to two
different
external USB hard drives? I just changed the assignment for one of these
drives. Now when I plug in the 200G drive, it is assigned letter G, and
when I plug in the 120G drive, it is assigned letter N.

Not surprisingly, when I plugged in my Drive N into a different computer,
it was assigned a different drive letter. Drive letter assignments are
specific to each computer.

Am I right about all this?

Easy way to look at it is a telephone answering service, the calls are
answered in the order they are initially received. Same with XP, giving
letters in that order. Some thumb drives default to much higher letters, W
for instance, out of the letter scheme used by most PCs.

My personal preference is to give onboard hard drive partitions sequential
letters, followed by other onboard stuff, then external devices, then CD/DVD
on the other end of the spectrum like S or T.