What karyonix reported seemed to me a completely different thing.
I.e. that part of the GUID (volume or also partition?) changed when a drive letter was assigned, then removed, then re-assigned to the same volume, being replaced by "different" values.
That could be a sort of dichotomy between a "plain" mount (or "first time" mount) and a mount/unmount/re-mount, but if karyonix cannto confiirm/explain clear the matter, I don't see how completely different experiments (like manually changing the GUID on disk) can confirm or refute that.
DISKPART> create partition primary size=100
DiskPart succeeded in creating the specified partition.
C:\tempo>dd bs=4096 count=1 if=\\.\PhysicalDrive1 of=pd1.bin
1+0 records in
1+0 records out
4096 bytes (4.1 kB) copied, 0 seconds, Infinity B/s
C:\tempo>hexdump -C pd1.bin
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001b0 00 00 00 00 00 00 00 00 57 f1 82 41 00 00 00 00 |........W?.A....|
000001c0 02 00 ee fe 3f 81 01 00 00 00 ff ff ff ff 00 00 |..?.?...........|
000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U?|
00000200 45 46 49 20 50 41 52 54 00 00 01 00 5c 00 00 00 |EFI PART....\...|
00000210 32 9d fb 22 00 00 00 00 01 00 00 00 00 00 00 00 |2.?"............|
00000220 ff ff 1f 00 00 00 00 00 22 00 00 00 00 00 00 00 |........".......|
00000230 de ff 1f 00 00 00 00 00 4c d1 7a 58 44 ba 00 4a |........L?zXD?.J|
00000240 b8 6e 9a 94 ed ba 60 01 02 00 00 00 00 00 00 00 |?n."??`.........|
00000250 80 00 00 00 80 00 00 00 81 ec d2 8d 00 00 00 00 |.........??.....|
00000260 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000400 16 e3 c9 e3 5c 0b b8 4d 81 7d f9 2d f0 02 15 ae |.???\.?M.}?-?..?|
00000410 ff 10 d4 ba 63 f5 c9 48 81 44 1c 99 5a 9e 9b fa |..??c??H.D..Z..?|
00000420 22 00 00 00 00 00 00 00 ff 7f 00 00 00 00 00 00 |"...............|
00000430 00 00 00 00 00 00 00 00 4d 00 69 00 63 00 72 00 |........M.i.c.r.|
00000440 6f 00 73 00 6f 00 66 00 74 00 20 00 72 00 65 00 |o.s.o.f.t. .r.e.|
00000450 73 00 65 00 72 00 76 00 65 00 64 00 20 00 70 00 |s.e.r.v.e.d. .p.|
00000460 61 00 72 00 74 00 69 00 74 00 69 00 6f 00 6e 00 |a.r.t.i.t.i.o.n.|
00000470 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000480 a2 a0 d0 eb e5 b9 33 44 87 c0 68 b6 b7 26 99 c7 |? ????3D.?h??&.?|
00000490 d4 e1 b3 f8 23 e9 b6 40 be 58 74 5e 1e 3e e1 63 |????#??@?Xt^.>?c|
000004a0 00 80 00 00 00 00 00 00 ff 9f 03 00 00 00 00 00 |................|
000004b0 00 00 00 00 00 00 00 80 42 00 61 00 73 00 69 00 |........B.a.s.i.|
000004c0 63 00 20 00 64 00 61 00 74 00 61 00 20 00 70 00 |c. .d.a.t.a. .p.|
000004d0 61 00 72 00 74 00 69 00 74 00 69 00 6f 00 6e 00 |a.r.t.i.t.i.o.n.|
000004e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001000
C:\tempo>mountvol
...
\\?\Volume{f8b3e1d4-e923-40b6-be58-745e1e3ee163}\
*** NO MOUNT POINTS ***
...
DISKPART> format fs=ntfs quick
100 percent completed
DiskPart successfully formatted the volume.
DISKPART> list partition
Partition ### Type Size Offset
------------- ---------------- ------- -------
Partition 1 Reserved 15 MB 17 KB
* Partition 2 Primary 100 MB 16 MB
DISKPART> detail partition
Partition 2
Type : ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
Hidden : No
Required: No
Attrib : 0X8000000000000000
Offset in Bytes: 16777216
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 2 NTFS Partition 100 MB Healthy
DISKPART> assign
DiskPart successfully assigned the drive letter or mount point.
C:\tempo>dd bs=4096 count=1 if=\\.\PhysicalDrive1 of=pd1.bin
1+0 records in
1+0 records out
4096 bytes (4.1 kB) copied, 0 seconds, Infinity B/s
C:\tempo>hexdump -C pd1.bin
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001b0 00 00 00 00 00 00 00 00 57 f1 82 41 00 00 00 00 |........W?.A....|
000001c0 02 00 ee fe 3f 81 01 00 00 00 ff ff ff ff 00 00 |..?.?...........|
000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U?|
00000200 45 46 49 20 50 41 52 54 00 00 01 00 5c 00 00 00 |EFI PART....\...|
00000210 1d 3f 65 d1 00 00 00 00 01 00 00 00 00 00 00 00 |.?e?............|
00000220 ff ff 1f 00 00 00 00 00 22 00 00 00 00 00 00 00 |........".......|
00000230 de ff 1f 00 00 00 00 00 4c d1 7a 58 44 ba 00 4a |........L?zXD?.J|
00000240 b8 6e 9a 94 ed ba 60 01 02 00 00 00 00 00 00 00 |?n."??`.........|
00000250 80 00 00 00 80 00 00 00 04 e7 25 80 00 00 00 00 |.........?%.....|
00000260 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000400 16 e3 c9 e3 5c 0b b8 4d 81 7d f9 2d f0 02 15 ae |.???\.?M.}?-?..?|
00000410 ff 10 d4 ba 63 f5 c9 48 81 44 1c 99 5a 9e 9b fa |..??c??H.D..Z..?|
00000420 22 00 00 00 00 00 00 00 ff 7f 00 00 00 00 00 00 |"...............|
00000430 00 00 00 00 00 00 00 00 4d 00 69 00 63 00 72 00 |........M.i.c.r.|
00000440 6f 00 73 00 6f 00 66 00 74 00 20 00 72 00 65 00 |o.s.o.f.t. .r.e.|
00000450 73 00 65 00 72 00 76 00 65 00 64 00 20 00 70 00 |s.e.r.v.e.d. .p.|
00000460 61 00 72 00 74 00 69 00 74 00 69 00 6f 00 6e 00 |a.r.t.i.t.i.o.n.|
00000470 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000480 a2 a0 d0 eb e5 b9 33 44 87 c0 68 b6 b7 26 99 c7 |? ????3D.?h??&.?|
00000490 d4 e1 b3 f8 23 e9 b6 40 be 58 74 5e 1e 3e e1 63 |????#??@?Xt^.>?c|
000004a0 00 80 00 00 00 00 00 00 ff 9f 03 00 00 00 00 00 |................|
000004b0 00 00 00 00 00 00 00 00 42 00 61 00 73 00 69 00 |........B.a.s.i.|
000004c0 63 00 20 00 64 00 61 00 74 00 61 00 20 00 70 00 |c. .d.a.t.a. .p.|
000004d0 61 00 72 00 74 00 69 00 74 00 69 00 6f 00 6e 00 |a.r.t.i.t.i.o.n.|
000004e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001000
C:\tempo>mountvol
...
\\?\Volume{f8b3e1d4-e923-40b6-be58-745e1e3ee163}\
D:\
...
C:\tempo>reg query hklm\system\mounteddevices
HKEY_LOCAL_MACHINE\system\mounteddevices
...
\DosDevices\D: REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
DISKPART> remove
DiskPart successfully removed the drive letter or mount point.
C:\tempo>mountvol
...
\\?\Volume{f8b3e1d4-e923-40b6-be58-745e1e3ee163}\
*** NO MOUNT POINTS ***
...
C:\tempo>reg query hklm\system\mounteddevices
HKEY_LOCAL_MACHINE\system\mounteddevices
...
#{18670fd9-44ca-11e9-ba59-080027e30448} REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
DISKPART> assign
DiskPart successfully assigned the drive letter or mount point.
C:\tempo>mountvol
...
\\?\Volume{f8b3e1d4-e923-40b6-be58-745e1e3ee163}\
D:\
...
C:\tempo>reg query hklm\system\mounteddevices
HKEY_LOCAL_MACHINE\system\mounteddevices
...
\DosDevices\D: REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
DISKPART> remove
DiskPart successfully removed the drive letter or mount point.
C:\tempo>reg query hklm\system\mounteddevices
HKEY_LOCAL_MACHINE\system\mounteddevices
...
#{186710aa-44ca-11e9-ba59-080027e30448} REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
DISKPART> assign
DiskPart successfully assigned the drive letter or mount point.
DISKPART> remove
DiskPart successfully removed the drive letter or mount point.
C:\tempo>reg query hklm\system\mounteddevices
HKEY_LOCAL_MACHINE\system\mounteddevices
...
#{186710b4-44ca-11e9-ba59-080027e30448} REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
DISKPART> assign
DiskPart successfully assigned the drive letter or mount point.
DISKPART> detail disk
...
Disk ID: {587AD14C-BA44-4A00-B86E-9A94EDBA6001}
...
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 2 D NTFS Partition 100 MB Healthy
DISKPART> detail partition
Partition 2
Type : ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
Hidden : No
Required: No
Attrib : 0000000000000000
Offset in Bytes: 16777216
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 2 D NTFS Partition 100 MB Healthy
C:\tempo>reg query hklm\system\mounteddevices
HKEY_LOCAL_MACHINE\system\mounteddevices
...
\DosDevices\D: REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
C:\tempo>mountvol
...
\\?\Volume{f8b3e1d4-e923-40b6-be58-745e1e3ee163}\
D:\
...
C:\tempo>ipconfig /all
...
Physical Address. . . . . . . . . : 08-00-27-E3-04-48
...
This registry value exists when drive letter D: is assigned to the test partition.
\DosDevices\D: REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
These registry values exist one at a time when drive letter is removed from the test partition
#{18670fd9-44ca-11e9-ba59-080027e30448} REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
#{186710aa-44ca-11e9-ba59-080027e30448} REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
#{186710b4-44ca-11e9-ba59-080027e30448} REG_BINARY 444D494F3A49443AD4E1B3F823E9B640BE58745E1E3EE163
They are deleted when drive letter is assigned.