Simon Kidd you wrote: “Sadly my PC completely misbehaved on me this evening (a windows update started …)”
This month Windows has a big update and that is why the problems came to people working with huge files. I would advise to search for a update each 16th of the month. Maybe you missed even the 1903 update and Windows is catching up.
How can you see this all. Go to START and right click your mouse> go to system> Look what version of Microsoft is running. You need to have 2004 and 19041.388. It is a big update for the rollout of May this year. Keep in mind to update in time. I do this each week, so that an update does not slow my machines.
To see if there are updates Go to START> left click go to settings (the little flower)> scroll down and push the button update.
Be aware that Windows is going to change in the coming time. For people running the 32 bits version it is going to be the end for Windows. The visualisation of pictograms is going to be more simple. Windows Edge will get his own logo. For those who have not seen it. this is the Dutch site: https://www.microsoft.com/nl-nl/edge
For people using PSP there will be not much change to use it, but programs like Office pro, Adobe Photoshop and 3D programs a videocart with power is needed (basic cart Nvidia RTX 2060) Dont worry but if you buy a second hand machine, look that it is a quad core. Best is with DDR4 memory, because DDR3 memory is running out. 2021/2022 will DDR 5 memory come to the market.
Please don’t worry with all this information and have fun as long as you can.