It would actually be better if somebody else would answer you. I have not
had Windows installed on the computers I administrate for many years. The
last Windows I used (apart from a few hours on computers I do not
administrate) was Windows XP. At that time, there was a CD to (re)install
Windows.
If I wanted to keep a pre-installed Windows, I would:
backup the user files (you should frequently do that anyway) simply copying
those files to another drive;
make some space (as explained in my previous post);
defrag the filesystem where space was made;
boot the Trisquel Live system;
shrink the filesystem in question with GParted (it is on the live system);
launch the Trisquel installer;
choose the installation type "Something else";
in the next step, define three partitions in the free space: one swap
partition (as large as your RAM), one where to mount / (24 GB, ext4, for
instance) and one where to mount (all the remaining space, XFS, for
instance);
end the installation.
The risky step for your Windows system is shrinking the filesystem it is
installed on. But I have never heard of any such problem. A power cut at
that moment may be bad though...
