Hi there - it is unsatisfying not really understanding what caused the problem is and why setting the fast boot resolves it! I'm just going to leave well enough alone but I'll respond to your last post FWIW
I had seen when I googled that InsydeH2O is supposed to be UEFI but I assumed that the one I have here must just be a much older, non-UEFI version because there are very few options to change and absolutely nothing about CSM or BIOS legacy.
The only options in the Security tab are the ability to set user, supervisor and HDD passwords, none of which had been registered. I even tried registering passwords to see if that might make more setup options appear, but no.
The advanced tab, other than the 'fast boot' which resolved the problem, only has the options you will see in the attached screenshot and the Boot screen is a list of devices - of which there are only the HDD and ODD - whose order you can swap. Nothing else!
As you say there would be other nonstandard firmware fixes but thankfully I won't need to go there.
Thanks again for helping me.
Jenny

I had seen when I googled that InsydeH2O is supposed to be UEFI but I assumed that the one I have here must just be a much older, non-UEFI version because there are very few options to change and absolutely nothing about CSM or BIOS legacy.
The only options in the Security tab are the ability to set user, supervisor and HDD passwords, none of which had been registered. I even tried registering passwords to see if that might make more setup options appear, but no.
The advanced tab, other than the 'fast boot' which resolved the problem, only has the options you will see in the attached screenshot and the Boot screen is a list of devices - of which there are only the HDD and ODD - whose order you can swap. Nothing else!
As you say there would be other nonstandard firmware fixes but thankfully I won't need to go there.
Thanks again for helping me.
Jenny