Finally I have a grep program that works. I had been using PRGrep 8.5 but it kept on coming up with errors if I gave it anything too challenging to do. For some reason I've never managed to get the grep style facility in Windows Explorer to work. Maybe it's the way that the dog wags its tail but it would just never find anything - even things that were definitely there.
I've loaded and run Agent Ransack (version 1.7.3) and this grep program found everything that I was looking for. I didn't challenge it but in time to come I will.
What has particularly surprised me while looking for a solid and free windows based grep utility is that there doesn't appear to be any out there. This is such an old requirement for any computer system that I would have thought that there would be several excellent utilities available with open source and a well supported community as there are with so many of the other essential utilities.
I can remember writing my own DOS version of grep in 1991 and could easily do the same again now but I don't want to spend several hours putting together what several hundred programmers must have already done and made available to everyone else.