I must apologize for not reporting back to the forum.
My problem was solved by getting PATH statements sorted out. After a reboot everything started working.
On Windows there are 2 PATH system variables. One is for user’s own account, other is a general one, for all accounts on that PC.
I put all the relevant paths into general PATH system variable, like this:
It is important to install Python 2.7.14 before you install PlatformIO, because PIO is written in Python. If PIO doesn’t know where Python is it can’t install itself.
As well, possibly maybe, Python doesn’t like white space " " character in the path, so maybe it its not a good idea to put Python installation into “c:\Program Files…” folder.
Don’t forget to put a semi-colon “;” on the end of each path string.