Please read this report with the topic 'Messed up my beautiful Mageia 5 install' under Basic Support.

I installed Mageia 5 directly after letting go of Ubuntu 16.04 LTS after a week of not really getting anywhere.  The very first time I used the installer, I was pleasantly surprised that Mageia will erase and reformat the disc entirely.  I have never opted for anthing else from the word go.  This not the case, but I was left under the impression that the disc was wiped of all previous content. 

@benmc suggested that my BIOS boot image may be damaged.  Followed that lead and got nowhere.  Topic has follow up reports.

Then after that I followed @doktor500's advice to do fdisk -l which revealed the cause of it all.  The disc is still, as I write here, formatted in Ubuntu's DOS format.

I am conversant and comfortable with DOS/UEFI issues.  This laptop was bought in 2013 with a gpt label all along.  Mageia 4 is now installed and works.

I suspect Mageia 5 not being able to install by reason of the incompatibility with the disc's dos formatting.

[root@localhost ~]# fdisk -l

Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device    Boot     Start        End    Blocks  Id System
/dev/sda1 *         2048   25189919  12593936  83 Linux
/dev/sda2       25192440 1953520064 964163812+  5 Extended
/dev/sda5       25192448   33367004   4087278+ 82 Linux swap / Solaris
/dev/sda6       33370112 1953520064 960074976+ 83 Linux