How does Win allocate drive letters?

[Stephen Ford]

WinXP SP2 (up to date with Win Update)

I have a problem where a third party device when plugged into a USB port
becomes accessible via a drive letter it creates and the drive letter
conflicts with an existing drive letter.

My PC has one HDD in three partitions and there is a CD drive. So the drive
letters are C:, D:, E: & F:

I use the following batch file at start up

echo on
subst H: D:\
subst J: D:\data
subst K: "D:\DATA\Acquire Home Services"
subst L: D:\DATA\Paradox
subst M: "D:\DATA\WP9 App data"
subst N: "C:\Documents and Settings\Office\Application
Data\Corel\PerfectExpert\9\Custom WP Templates"
Pause
exit

When the device is plugged in it creates "Removable Disk (G" &
"TomTom(H". the H: conflicts with the H: drive created by the batch file.
Yes, it's a TomTom sat.nav.

My initial discussion with TomTom support resulted in the comment "it's
Windows that creates the drive and causes the conflict, not TomTom". I can
believe it's feasible but I wonder if there is such a hole in the O/S such
that it tramples over drives created by the SUBST command. What might be
going on?

 

[vista terminal ator]

you can change the letters of hdd and cdroms and external devices from

control panel, administrative tools, computer managment, disk managment.

right click on the one you want and give it another letter...

I suggest you change the letters of the conflicting devices to somthing like
m, n, o, p so you can leave letter-space for the removable device you add
later

 

[Stephen Ford]

Thanks for that.

I've just discovered elsewhere that removeable drive letters created when a
removable device is connected can conflict with non-hardware drive letters
(eg as created by network systems or the SUBST command).

So as you say, I need to move my non-hardware drive letters further up the
alphabet to leave room for removable drive letters. It would be nice if
Windows coped with this automatically.

 

[Uwe Sieber]

It scans from C: upwards for the first availlable letter.
XP doesn't care about subst and net drive letters here.
Vista does but if you attach an USB drive for the first
time before your subst drives are created it may assing
a letter intended as subst drive, so the subst command
will fail later.

Either let some low letters unused for external drives
or install my tool 'USB drive letter manager'. Here
you can reserve you subst drive letters so they are
never used for othter drives.
http://www.uwe-sieber.de/usbdlm_e.html

You need an USBDLM.INI like this:

[ExcludedLetters]
Letter1=H
Letter2=J
Letter3=K
Letter4=L
Letter5=M
Letter6=N

Or define default letters for USB drives:

[DriveLetters]
Letter1=O
Letter2=P
Letter3=Q
Letter4=R
Letter5=S
Letter6=T


Greetings from Germany

Uwe

 

[Stephen Ford]

Hi Uwe

A fantastic product! It might be small and simple (although I couldn't write
it) but it does the job; It does what you say it does and it has enabled me
to connect my TomTom without changing my list of drive letters on my PC.
Phew, thank goodness!

I'm amazed by the unhelpfulness of TomTom (not a small company!). They have
just replied to my support request by saying they can;'t help. They have not
even explained the problem with Windows and suggested a route (and do they
know about finding routes*!?) for me to take in my search for a solution.

My search this morning has resulted in finding your product (or did you find
me ) and a number of other interested people. I am going to post your
details on the Expansis.com web site where I have had some help and I will
give all your details to TomTom.

I have purchased a licence.

Good luck with your other business ideas.

 

[Stephen Ford]

I hope you don't mind me helping with some words in your reply.

The word "assing" needs to be "assign" (typo I think...), and the word "let"
in "Either let some low letters .." needs to be "leave" ie "Either leave
some low letters .."

HTH
--
Regards
Stephen Ford

It scans from C: upwards for the first availlable letter.
XP doesn't care about subst and net drive letters here.
Vista does but if you attach an USB drive for the first
time before your subst drives are created it may assing
a letter intended as subst drive, so the subst command
will fail later.

Either let some low letters unused for external drives
or install my tool 'USB drive letter manager'. Here
you can reserve you subst drive letters so they are
never used for othter drives.
http://www.uwe-sieber.de/usbdlm_e.html

You need an USBDLM.INI like this:

[ExcludedLetters]
Letter1=H
Letter2=J
Letter3=K
Letter4=L
Letter5=M
Letter6=N

Or define default letters for USB drives:

[DriveLetters]
Letter1=O
Letter2=P
Letter3=Q
Letter4=R
Letter5=S
Letter6=T


Greetings from Germany

Uwe

WinXP SP2 (up to date with Win Update)

I have a problem where a third party device when plugged into a USB port
becomes accessible via a drive letter it creates and the drive letter
conflicts with an existing drive letter.

My PC has one HDD in three partitions and there is a CD drive. So the
drive letters are C:, D:, E: & F:

I use the following batch file at start up

echo on
subst H: D:\
subst J: D:\data
subst K: "D:\DATA\Acquire Home Services"
subst L: D:\DATA\Paradox
subst M: "D:\DATA\WP9 App data"
subst N: "C:\Documents and Settings\Office\Application
Data\Corel\PerfectExpert\9\Custom WP Templates"
Pause
exit

When the device is plugged in it creates "Removable Disk (G" &
"TomTom(H". the H: conflicts with the H: drive created by the batch
file. Yes, it's a TomTom sat.nav.

My initial discussion with TomTom support resulted in the comment "it's
Windows that creates the drive and causes the conflict, not TomTom". I
can believe it's feasible but I wonder if there is such a hole in the O/S
such that it tramples over drives created by the SUBST command. What
might be going on?

 

[Bob I]

Left to it's own, XP automatically assigns Local drive letters
(non-floppy) starting with C: and working up. Network drive letters will
be automaticaly assigned starting with Z: and working their way down. IF
someone starts assigning letters manually, then they take the
responsibility of sorting out the conflicts.

 

[Stephen Ford]

I use the batch file to create a standard look and feel to my PCs. All s/w
is then configured the same. I don't know if there is a better way. It cause
this removable disc prob though. USBDLM seems to have solved that.

 

[Uwe Sieber]

Thanks

 

[GO]

Left to it's own, XP automatically assigns Local drive letters
(non-floppy) starting with C: and working up. Network drive letters
will be automaticaly assigned starting with Z: and working their way
down. IF someone starts assigning letters manually, then they take the
responsibility of sorting out the conflicts.

I'm curious though as to why the OS can't sort out these conflicts? I
realize it's a different mechanism for assigning a drive letter to a
physical hard drive than mapping a network share (or even using the subst
command), but you wouldn't think it'd be that hard for the OS to check if
that particular letter is in use. The OS has to know at some level that
it's in use or not.

 

[Stephen Ford]

I'm curious though as to why the OS can't sort out these conflicts? I

realize it's a different mechanism for assigning a drive letter to a
physical hard drive than mapping a network share (or even using the subst
command), but you wouldn't think it'd be that hard for the OS to check if
that particular letter is in use. The OS has to know at some level that
it's in use or not.

Well exactly. I mean, MS have built and entire O/S - so they must know
something about this sort of issue. You say "I realize it's a different
mechanism for assigning a drive letter ..." - I don't have clue how this is
done - not my field at all, but in the end the process for look for drives
must be able to sense "a drive letter" whatever it's type (I mean isn't this
C++'s forte?) and if it exists then (surely) don't trample over it...

 

[Uwe Sieber]

Well exactly. I mean, MS have built and entire O/S - so they must know
something about this sort of issue. You say "I realize it's a different
mechanism for assigning a drive letter ..." - I don't have clue how this is
done - not my field at all, but in the end the process for look for drives
must be able to sense "a drive letter" whatever it's type (I mean isn't this
C++'s forte?) and if it exists then (surely) don't trample over it...

The problem came with XP. Under Windows 2000 subst and network drives
where global objects. Under XP they have been moved into the context
of the user, so multiple users logged on using the XP fast user
switching can have different subst and network drives.

They just fogot to consider this in the volume manager. Shit happens.



Uwe

 

[Lil' Dave]

WinXP SP2 (up to date with Win Update)

I have a problem where a third party device when plugged into a USB port
becomes accessible via a drive letter it creates and the drive letter
conflicts with an existing drive letter.

My PC has one HDD in three partitions and there is a CD drive. So the
drive letters are C:, D:, E: & F:

I use the following batch file at start up

echo on
subst H: D:\
subst J: D:\data
subst K: "D:\DATA\Acquire Home Services"
subst L: D:\DATA\Paradox
subst M: "D:\DATA\WP9 App data"
subst N: "C:\Documents and Settings\Office\Application
Data\Corel\PerfectExpert\9\Custom WP Templates"
Pause
exit

When the device is plugged in it creates "Removable Disk (G" &
"TomTom(H". the H: conflicts with the H: drive created by the batch
file. Yes, it's a TomTom sat.nav.

My initial discussion with TomTom support resulted in the comment "it's
Windows that creates the drive and causes the conflict, not TomTom". I can
believe it's feasible but I wonder if there is such a hole in the O/S such
that it tramples over drives created by the SUBST command. What might be
going on?

My experience: XP assigns "drive" letters on first come/first serve basis
beginning at installation time. The former hierarchy that msdos had used is
no longer valid in XP. That's why as soon as the XP install is done, I
assign a letter like "S" or "T" to a CD or DVD device. Reassign any other
partition lettering as well at that time in accordance with the msdos drive
hierarchy as this is very familiar to me. The only thing I don't bother
myself with in my USB thumb drive that takes "W".

If I were to assign a folder a "drive" letter, I would do the same thing as
above. Then, assign subsequent letters to each folder.
Dave

 

[Paul Randall]

Maybe each OS keeps doing the same wrong thing to maintain compatibility
with the previous OS. By now there could be millions of people relying on
this behavior.

-Paul Randall

 

[GO]

Paul Randall wrote:
Maybe each OS keeps doing the same wrong thing to maintain
compatibility with the previous OS. By now there could be millions
of people relying on this behavior.

-Paul Randall

I understand what you're saying and in some contexts it would make some
sense. However, in this case I don't quite understand how anyone could be
relying on this type of behavior? Why would anyone want Windows to take
over drive letter when it's already in use by you and/or the system.

 

[Paul Randall]

I understand what you're saying and in some contexts it would make some
sense. However, in this case I don't quite understand how anyone could be
relying on this type of behavior? Why would anyone want Windows to take
over drive letter when it's already in use by you and/or the system.

Your last sentence indicates you got the point of my backhanded statement.
How do nasty little things like this not get fixed generation after
generation? By accident? By not knowing the problem exists? By wanting it
not to get fixed?

-Paul Randall

 

[GO]

Your last sentence indicates you got the point of my backhanded
statement. How do nasty little things like this not get fixed
generation after generation? By accident? By not knowing the
problem exists? By wanting it not to get fixed?

-Paul Randall

Aaaah....sarcasm eh? Gotcha. My apologies. I thought you were being
serious....I'm getting too used to the flamewars going on over in the Vista
group.