We have lots of computers - my husband's business used them to control communications for the emergency services.

Some have upgraded to W 10 first try, others, like the one I am using, will download and attempt to install, then fail.

As he is winding up the company at the end of this month there are lots of bits and pieces around which can be put together to make up a working PC.
It seems strange that this one, which is fairly new with W 8.1 and has several truly humungous disks which have swallowed the contents of several older PCs and barely show double figures of fullness, will not upgrade, but a cobbled together box of the best bits off the shelves at the end of the workshop - no bother.