wow - a very comprehensive answer. However it seems I have now got it correctly reinstalled with the correct environment and path (as below) So I'm back to my original problem:
C:\Users\Nick>python -m idlelib ** IDLE can't import Tkinter. Your Python may not be configured for Tk. ** On doing a repair or modify to install tcl/Tk again, the same result. C:\Users\Nick>python -c "import sys; print(*sys.path, sep='\n')" gives C:\Python\Python35\python35.zip C:\Python\Python35\DLLs C:\Python\Python35\lib C:\Python\Python35 C:\Python\Python35\lib\site-packages This looks OK, Python35 directory contains Lib and tcl as it does on my now working Win7 system, and Lib contains tkinter C:\Users\Nick>path PATH=C:\Python\Python35\Scripts\;C:\Python\Python35\;C:\ProgramData\Oracle\Java\javapath;C:\Program Files\Broadcom\Broadcom 802.11 Network Adapter;;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\ATI Technologies\ATI.ACE\Core-Static; -- https://mail.python.org/mailman/listinfo/python-list
