John, I have already placed a copy of the file in the SysWOW64 directory so that wasn't the issue. I did however realize I did not run the command regsvr32...... in admin mode so tried that and the command was then successful.
However, no joy until I unzipped Fig XP into C:\Program Files (x86)\FigureXP as you suggested, then it worked! (trying to execute the program from the .../Downloads/FigureXP directory resulted in nothing happening - no error message or anything else).
Anyhow, all good now - thanks much for the help.
Edit: Tried running it from the Downloads/FigureXP directory again and now it works.
Edit 2: Spoke too soon again - now the original problem I had with my Win 7 install (my .fig files not appearing in Windows Explorer in the folder where the .exe resides) shows up in the Win 10 install as well.
So, tried Mike's suggestion and searched for the file name and the files turned up in:
C:\Users\....\AppData\Local\VirtualStore\Program Files (x86)\FigureXP
All considered, I think FigureXP could use a bit of upgrade work at least for for Win 7 & 10 systems.....!
Edited by nosmoke, 11 November 2019 - 07:20 PM.