A huge thank you Mackavi,
I have solved most of my problems. Probably a sledgehammer approach but I completely refreshed Windows 10. Unfortunately because the update and security button did not work I had to go directly to the reset page. As what I did worked well and my computer now seems more sprightly than even when new I will describe each step.
I accessed the trouble shoot button via Windows key > Power -> then hold shift and click restart -> refresh PC. I actually chose to refresh my laptop with the option that removes all non-windows apps.
The machine then restored itself. I reinstalled Opus 9.75 and noticed that Win10 was now fully functional (I should note that I think the main problem was that my SSD needed clearing - the reason for this was that for convenience I had saved my presentation, which had a lot of video, to the desktop. So as part of this exercise I cleared out a lot of material from the SSD).
However, I still had issues with video in Opus (the videos would start ok but then would 'hang' after around 30secs), to overcome this I took another sledgehammer route and installed the Cole2K Advanced Codec pack, now everything AVI, MP4 and WMV play smoothly and without a hiccup.
I have looked at several sources to see if the Cole2K codec packs have any issues and it seems that if you get the pack directly from the cole2k site there are no issues see
http://codec-pack-advanced.en.lo4d.com/ ... ware-tests (am I allowed to put links in these pages?) and also MajorGeeks and all the sites report the codec pack free of malware, ads, etc. etc.
So now I have a fully working laptop, albeit I need to reinstall my main programs (which will all now be the latest release), but that is a small price for such a smooth running machine (you could choose the refresh option that retains the software). I will wait until after this evening before I add anything else to my machine.
I have let the presentation run several times and it runs absolutely smoothly so very pleased.
Now looking forward to using the presentation this evening - fingers crossed!
M