"Install Ubuntu alongside Windows boot manager" not showing when Installing in Legacy Mode

I'm trying to install Ubuntu 16.04.1 in a dual-boot configuration. I read a few articles online and questions in Ask Ubuntu, but couldn't understand why the option "Install Ubuntu alongside Windows boot manager" doesn't show up in the installer.

Steps taken:

1. The Ubuntu image was installed on a DOK via Universal USB Installer.
2. Safe boot and fast boot were disabled in the BIOS.
3. Fast boot was disabled in Windows's Power Options.
4. A partition was made for Ubuntu through Windows, and was formatted to NTFS.

General Information:

1. HP Elitebook 840 G3
2. Windows 10 that was installed on top of Windows 7 in Legacy Mode.

When I choose "Something else" in the installer, the sizes of the drives don't add up like in Disk Management under Windows. I don't have enough reputation to embed pictures in the post, so I'll just list the drives and numbers:

Windows disk management

1. Windows (C:), Simple, Dynamic, NTFS, 330.5GB
2. HP_RECOVERY(D:), Simple, Dynamic, NTFS, 19,53GB
3. HP_TOOLS (E:), Simple, Dynamic, NTFS, 1.95GB
4. SYSTEM, Simple, Dynamic, NTFS, 1GB
5. Ubuntu (F:), Dynamic, Simple, NTFS, 123.96GB

Ubuntu installer

1. /dev/sda
2. /dev/sda1, 1MB, unknown, Windows 10 (loader)
3. /dev/sda2, 1074MB, unknown, Windows 7 (loader)
4. /dev/sda3, 354866MB, 17529MB
5. /dev/sda4, 156166MB, 80MB

What's weird is that my D\E drives under windows don't show in the Ubuntu installer, but seem like they get counted with either C or F drives (not sure which one, both seem reasonable).

So, the question: is there a way to get the "install alongside Windows" option to appear, and if not, how should I use the "something else" option without wrecking my laptop?

Solution 1:

I don't know much about Windows dynamic partitions except that I should avoid them for linux.

The drive space where you want to install Ubuntu can be treated this way

Boot into Windows

• Remove the partition and leave the drive space as unallocated. From your question I guess this is it:

  Ubuntu (F:), Dynamic, Simple, NTFS, 123.96GB
  

Boot into the Ubuntu boot drive (USB or DVD)

• Alternative 1:

  • Start gparted and create partitions for Ubuntu: One big partition for the root file system and one small partition for swap. You can let the installer create the file system alias 'format the partition'. If you want to create it manually, I suggest ext4 for the root partition.
  • Start the installer and at the partitioning window select Something else and select the partitions you created with gparted.

• Alternative 2:

  • Start the installer and let it find the unallocated drive space. You must check very carefully, that it really finds and selects this space, because it might not see Windows and suggest to overwrite it. So this alternative is more risky. (Here you might or might not see 'Install alongside').

Solution 2:

I had the same problem and the issue was that I couldn't have more than 4 partitions in my hard drive.
In my case, I was trying to install Ubuntu 20 with Windows 10, but actually, it's a similar case.

https://forums.linuxmint.com/viewtopic.php?t=287093