The issue is that I don't know how many GB it still really needs (even if I saw the value of 160GB globally on some sites) 
I had 120GB free few weeks ago on my "Windows C:" disk with Armory already uptodate and now I have only 4Go on this disk ...
My %APPDATA%/Roaming/Bitcoin directory is currently around 117GB

I'm going to move it on a new disk. How can I do it properly without restarting from scratch, knowing that Bitcoin core node is currently updating ?