Xubuntu install on Win7 laptop fails

[MR ZenWiz]

On Fri, Jul 7, 2017 at 11:02 PM, Ralf Mardorf <silver.bullet at zoho.com> wrote:
>
> Hi,
>
> first mount all partitions, then list the content of all partitions.
>
> ls -hAl /mnt/point_boot/grub/ /mnt/point_2/ /mnt/point_n/
>
> Assuming there should be a Windows that looks good and a Linux,
> including /boot/grub/ files, you could install grub like this
>
>     sudo grub-install --boot-directory=/mnt/point_boot/grub/ /dev/sda
>
> after updating grub, there likely would be a GRUB menu with a
> chainloader to boot Windows, as well as the appropriate Ubuntu entries.
> But I suspect you even don't need to run update-grub, grub-mkconfig or
> whatever the command is named. I suspect you installed grub to an
> Ubuntu partition instead of just /dev/sda without a number, so just
> running grub-install might do the trick.
>
Update:

I discovered that the only way to control the boot sequence was on the
laptop's native screen, so that piece cleared up (it doesn't show on
the dock-station connected monitors).

The file systems looked fine, so I did the grub-install to no effect.
The laptop still boots straight into Windows.

I looked at the partition layout and this might be part of it:

Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 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: gpt
Disk identifier: F3DB32EB-3851-4CC0-A57E-0B50C27DC6F3

Device         Start       End   Sectors   Size Type
/dev/sda1       2048    206847    204800   100M EFI System
/dev/sda2     206848    468991    262144   128M Microsoft reserved
/dev/sda3     468992 502231039 501762048 239.3G Microsoft basic data
/dev/sda4  943554560 976773119  33218560  15.9G Microsoft basic data
/dev/sda5  502231040 502233087      2048     1M BIOS boot
/dev/sda6  502233088 935806975 433573888 206.8G Linux filesystem
/dev/sda7  935806976 943554559   7747584   3.7G Linux swap

Partition table entries are not in disk order.

Xubuntu install partitions 5, 6 and 7, and 5 appears to be completely
useless (that piece should be at the front of the disk).

I tried removing those partitions, but the installer can't seem to get
past there being an OS there and won't overwrite just those
partitions.

I'll try again after using gparted to reset those 3, but I'm not
messing with the Windows partitions at all unless there's a safe way
to do that.

MR