Thanks for the quick response. I should add that I started in computing exactly 50 years ago this month, going on a FORTRAN programming course as a geophysics doctoral research student. So I know how to program (nowadays in Python) and generally keep my various PCs and Linux machines running over the years, but this is the very first time I've had to ask for online help! I do have some big gaps in my knowledge, including neglecting to have applied updates to Win 7 over the last 7 years. Now I'm in trouble.
Anyway I ran chkdsk (a 500 GB disk, took about 10 minutes), then tried to run ListChkdskResult.exe as admin. I get a Win script host error window saying:
C: ...Temp\RarSFX1\ListChkdskResult.vbe
Line: 1
Char: 910
Error: 0x80041001
Code 80041001
Source: Null
The text file is on my desktop, but is empty.
What next?