I tried Driver Booster - remember, it is very difficult to get an app to run with this problem - either it runs at a tiny fraction of the speed it should run, or it doesn't run at all. Driver Booster started installing, got one thing done after a while,
then started showing a second one, but was stuck at 1% for 20-30 minutes. I had the idea of booting into safe mode, which is a lot harder to do these days. Anyhow, in safe mode there was no trace of the problem.
In Safe Mode, Driver Booster started installing, but it was stuck on Gigabit Network Controller, at 1%. After a while, it must have given up and moved on. When it finished, it said that three weren't updated: Gigabit Network Controller, Realtek High Definition
Audio, and Nvidia High Definition Audio. LatencyMon complained about the audio driver.
I rebooted normally and then Driver Booster was able to update these three. I rebooted, but after 6 minutes, the problem was back.
But what about the two audio drivers - do I need both? Could they be fighting with each other? I don't need audio on that computer at all - can I disable them?
Also, it happens that I've already ordered a evga video card to replace the nvidia one.
(After working on this problem 40-50 hours this week, I'm to tired to do the HD swap tonight.)