First of all, have you deleted Trisquel's install from the external disk, as
I suggested in
https://trisquel.info/forum/13aug2017-buy-trisquel-laptop?page=1#comment-120112
? You should. GParted is pretty user-friendly: right click on the row
corresponding to the partitions you want to affect and choose in the
contextual menu what you want to do: "delete", "resize", etc. The only
(significant!) risk is to err affect the wrong partition. Double-check that
the partition you will affect is the one you want to affect.
Then, I suggest you to backup your important files on that external disk (or
another one). Indeed, having the backup right next to the original data
(inside the same computer) is risky. Imagine that computer is stolen or
catch fire: you lose everything.
The complexity of your computer (so many drives and partitions) apparently
confuses Trisquel's installer that ended up installing on the external drive.
That is why I suggest you to not choose an automatic partitioning (such as
"Install Trisquel alongside Windows") but rather "Something else" (it is one
of the option the installer proposes). You will end up on a GParted-like
interface where you can delete, resize, create, format, etc. partitions on
your disks and define how Trisquel will use these partitions.
One single partition is mandatory: where / (the root of the file hierarchy)
will be mounted. Nevertheless, I strongly suggest two additional partitions
(as in the default partitioning scheme): one where /home will be mounted (it
will contain all user files; without that separate partition, they would be
on the same partition as /, i.e., with the system) and a swap partition
(known as "virtual memory" on Windows, i.e., an extension of the RAM). These
partitions can be (or not) on three different drives, if you wish. You only
need enough free space for each of them (after resizing the existing
partitions, what only is possible if they are not too full).
I suggested in
https://trisquel.info/forum/13aug2017-buy-trisquel-laptop#comment-119913 24
GB for the partition where / will be mounted (enough for the sole system,
unless you plan to install many space-consuming games), as much swap as you
have RAM (so that you can hibernate Trisquel, if you wish) and as much space
as possible for the partition where /home will be mounted (so that you can
have many large user files such as movies, pictures, etc.). So, before
launching the installer, you need to choose on what drive(s) you will create
those three partitions. It is your call. Having / on an SSD is good: the
system is faster (to boot in particular). However, your SSD is almost full.
At the creation of new partitions (in the free space you get after shrinking
existing existing partitions), you will have to tell (a drop-down menu) the
type of the partition. For the swap it is "linux-swap". For the partition
where to mount / I suggest ext4. For the partition where to mount /home I
suggest xfs. Those are the choices the default install makes too (I can
argue why these choices are good, if you wish, but I doubt you care).
Once the three partition created, their types chosen (click their "format"
check box they are not checked), the mount points (/ and /home, the swap is
not "mounted"), you can proceed with the rest of the installation that you
have already seen (defining the name of the system, your user name, your time
zone, etc.).
Let us hope the bootloader (GRUB) will not raise any trouble. If not, a
reboot (do not forget to unplug the USB key with the live system when the
computers starts booting) should bring you a menu where Trisquel is the
default system to boot but where you can choose to boot Windows too.
