To illustrate post above about "hidden" volumes or rather "not mountable" partitions.
Disk 2 is a GPT disks with 2 partitions.
Still, the first partition does not appear under partitions nor under volumes.
This first Partition (i.e harddisk2\partition1) is of type "SYSTEM" (C12A7328-F81F-11D2-BA4B-00A0C93EC93B) which "by the book" means it is not mountable.
Still, I could do vmount-win64 assign x: \device\harddisk2\partition1 (as a dos device) and use x: while in my dos "session".
By the way, I believe winntsetup uses that trick to map EFI FAT32 partitions.
But I could not do vmount-win64 assign x:\ \\?\Volume{GUID}\ (as a volume) as this partition does not have a volume guid.
The only way to use this partition as a volume would be to change its part type with vmount-win64 changeparttypegpt (touched here).
>vmount-win64 disks DiskNr;SN;ProductId;Size;Type;Removable 0;[01020304];WDC_WDS120G2G0A-00JH30;114480MB;SATA;NON-REMOVABLE 1;[56B682DC];Hitachi_HDP725016GLA380;152627MB;SATA;NON-REMOVABLE 2;[56B682DC];Virtual_Disk;256MB;UNKNOWN;NON-REMOVABLE >vmount-win64 partitions Drive;VolName;FS;Device;Size C:;[SYSTEME];NTFS;\device\harddisk0\partition2;114126MB E:;[DATA];NTFS;\device\harddisk1\partition1;152624MB F:;[];NTFS;\device\harddisk2\partition2;126MB R:;[RAMDRIVE];NTFS;\device\imdisk0;1023MB >vmount-win64 volumes VolumeGuid;Drive \\?\Volume{e26e7b15-122a-11e7-82bf-806e6f6e6963}\; \\?\Volume{876ebd81-ce10-11e8-8334-94de80c2a41e}\;E:\ \\?\Volume{6c53b84d-7eee-11e9-8347-94de80c2a41e}\;F:\ \\?\Volume{e26e7b16-122a-11e7-82bf-806e6f6e6963}\;C:\ \\?\Volume{1b04c823-6f36-11e9-8347-94de80c2a41e}\; \\?\Volume{1b04cb1f-6f36-11e9-8347-94de80c2a41e}\; \\?\Volume{05852cdd-6f3f-11e9-8347-94de80c2a41e}\; \\?\Volume{25a1075f-6f54-11e9-8347-94de80c2a41e}\; \\?\Volume{c3ccf19b-9cbc-11e8-8325-806e6f6e6963}\;D:\ >vmount-win64 devices Device;Drive \device\harddisk2\partition1; \device\harddisk2\partition2;F: \device\harddisk0\partition1; \device\harddisk0\partition2;C: \device\harddisk1\partition1;E: >vmount-win64 disklayout 2 PartNr;StartingOffset;PartLength;PartId;PartType;PartAttributes 1;65536;134217728;{6C53B84B-7EEE-11E9-8347-94DE80C2A41E} {C12A7328-F81F-11D2-BA4B-00A0C93EC93B} 0x00000000000000 00 2;134283264;133169152;{6C53B84D-7EEE-11E9-8347-94DE80C2A41E} {EBD0A0A2-B9E5-4433-87C0-68B6B72699C7} 0x00000000000000 00