AFter reboot, IDLE started, loaded the program I tried to run
previously, and ran it several times.  I closed the edit window and when
I closed the shell window, got same message.  The first box is titled
Microsoft Visual C++ Runtime Library.  After listing ...pythonw.exe, it says

"This program has asked the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information."

This time there is no second red-circle-X box but a Send Error Report to
Microsoft box.  That leads to Error Signature
AppName: pythonw.exe	 AppVer: 0.0.0.0	 ModName: tcl84.dll
ModVer: 8.4.2.16	 Offset: 00058cef

More testing: If I open the shell and do stuff interactively and close,
it closes ok as far as I have tested.  If I open the shell and an edit
window and close both, either order, even without running anything, then
it crashes on the second close.  I tried more than one file with the
same result.