I had a Lenovo which had a hidden Q partition (I think, I deleted the partition years ago). I had to change the partition id to 7 so I could change the drive letter (even though it was hidden) to install Office as Office click to run used a Q:\ while it was installing.
Have a look in diskpart and see what the partition ID is. 07 is Microsoft Basic Data, 17 is hidden, 27 is OEM recovery but there is a
whole bunch of them. Could be the dell software changes the partition id to something mountable - I know there are
Lenovo utilities to do this.
Perhaps you could have a look at or post the output of diskpart like the output below but adding
select partition 5 ,
detail partition as you have more partitions than me.
If you want you can use
setid = 07 (or whatever value) after selecting your partition to make them visible (or not). There isn't any risk in doing this really but note down what it was before you change it so you can change it back as your recovery won't work if you change it to something Windows knows nothing about.
Code:
C:\WINDOWS\system32>diskpart
Microsoft DiskPart version 10.0.9926
Copyright (C) 1999-2013 Microsoft Corporation.
On computer: WINDOWS10
DISKPART> select disk 0
Disk 0 is now the selected disk.
DISKPART> list partition
Partition ### Type Size Offset
------------- ---------------- ------- -------
Partition 1 Primary 200 MB 512 B
Partition 2 Primary 50 GB 200 MB
Partition 3 Primary 619 MB 50 GB
Partition 4 Primary 61 GB 51 GB
DISKPART> select partition 1
Partition 1 is now the selected partition.
DISKPART> detail partition
Partition 1
[COLOR=#ff0000]Type : EE[/COLOR]
Hidden: Yes
Active: No
Offset in Bytes: 512
There is no volume associated with this partition.
DISKPART> select partition 2
Partition 2 is now the selected partition.
DISKPART> detail partition
Partition 2
[COLOR=#ff0000]Type : 07[/COLOR]
Hidden: No
Active: No
Offset in Bytes: 209735680
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 0 Y Yosemite HFS P Partition 50 GB Healthy
DISKPART> select partition 3
Partition 3 is now the selected partition.
DISKPART> detail partition
Partition 3
[COLOR=#ff0000]Type : AB[/COLOR]
Hidden: Yes
Active: No
Offset in Bytes: 54682804224
There is no volume associated with this partition.
DISKPART> select partition 4
Partition 4 is now the selected partition.
DISKPART> detail partition
Partition 4
[COLOR=#ff0000]Type : 07[/COLOR]
Hidden: No
Active: Yes
Offset in Bytes: 55333355520
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 1 C Windows10 NTFS Partition 61 GB Healthy System
DISKPART> exit
Leaving DiskPart...
C:\WINDOWS\system32>