I'll never learn!
Still searching for fewer pauses and less blurries, I fell for the temptation to install the latest drivers. Nvidia drivers are supposed tp insta;ll without the need to remove earlier versions.
Anyway, I installed the latest, whose name I'm glad to have forgotten. Result, in the middle of the bootup there was the merest flash of a dreaded blue screen, failure, another attempt etc. In the absence of Windows I can't see how to do a Restore, to get me out of the mire. Next problem, I can't accept an offer to start up in safe mode, Most Recent, etc, 'cos a wireless keyboard doesn't work until the system has booted up......
Eventually dug out a wired keyboard and managed to accet the offer of starting in the most recent effective mode. That got me in, so I've now restored to yesterday's settings and hope it's going to be OK.
Meanwhile I'd spent a couple of hours removing and re inserting the two new memory sticks. They are now found by everything but Sandra, which tells me two slots are empty, when I can clearly see they are not. Just can't get the staff, these days.