edit: take a look at this:
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maybe you can disable the automount in diskpart.exe? I am not sure what will help remove the bogus drive assignments if diskpart can no longer do it.
i was thinking of deleting the bogus drive letters, then turn off the automount and rebooting. otherwise we would have to figure out where this is being done and change it there. (offline registry edit?)
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look at this diskpart.exe command
DISKPART> help automount
Enables or disables the automount feature.
Syntax: AUTOMOUNT [ENABLE] [DISABLE] [SCRUB] [NOERR]
ENABLE Enables Windows to automatically assign drive letters
to volumes that are added to the system.
DISABLE Prevents Windows from automatically assigning drive letters
to volumes that are added to the system.
SCRUB Removes mounted folder pathnames, drive letters, mounted
folder directories, and registry settings, for volumes that
are no longer in the system. This prevents volumes that were
previously in the system from being automatically assigned
their former drive letters and mounted folder pathnames when
they are reintroduced to the system.
NOERR For scripting only. When an error is encountered, DiskPart
continues to process commands as if the error did not occur.
Without the NOERR parameter, an error causes DiskPart to exit
with an error code.
When the AutoMount feature is enabled (the default on some versions
of Windows Server), Windows automatically brings the volume online,
and, assigns a drive letter and a volume GUID pathname to the volume,
when the volume is added to the system. In storage area network (SAN)
configurations, disabling AutoMount prevents Windows from automatically
onlining the volume and assigning drive letters or volume GUID pathnames
to any new volumes that are visible to the system.
Note that the AutoMount feature could only be applied to basic disk
volumes on Windows versions released prior to Windows Vista. Starting
with Windows Vista, the AutoMount feature can be applied to both basic
and dynamic disk volumes.
Example:
AUTOMOUNT
AUTOMOUNT ENABLE
AUTOMOUNT DISABLE
DISKPART>