My brother’s HP laptop (not a computer geek 
) win 10 drive quit responding , so I took it out and hooked it up to my Linux machine. Disks was able to see all the partitions, but also to see that there was only 7mb of free space. I could not read it at all.
I tested the HP by installing an old win 7 spinner I had, and it works fine, so I’ve got a new ssd coming to get the laptop up for him.
What software can I look for to recover his user files? Or any other tricks you’ve learned?
Once you have the LT up and running smoothly, you can add the faulty drive as a secondary (using USB adapter, whatever).
If the system will not read it, the issue could be unrecoverable using the usual methods.
You might try to locate a sector reader but that could be much more of a challenge than the data is worth.
There are third party companies that might be able to help such as rossman group in NY.
Best of luck and let us know how you fair.
As soon as the new ssd arrives, and is set up, that’s what I’ll do…
Hopefully it’s readable, but if not, it’s a “learning experience.” I’ll impress upon him to not stuff the system drive quite so full 
I suggest you start by deleting any files/folders that are not needed to free up some space.
It’s never good to try to stuff a HDD of any kind. 80% is pretty much the upper limit. Tell him to think of it like a car. You need to leave room for the driver to sit comfortably.
You might try installing the problem disk in a machine, but booting with the “System Rescue CD” https://www.system-rescue-cd.org/ and using it to access the problem drive… The programs on the disk are pretty good at reading and manipulating almost any known disk format, so might be useful at giving access to the disk so you can filter some of the not needed material to free up space…
ex-Gooserider
Also sounds like a very good strategy, thanks much!