Thanks, Steve and ATR, for your suggestions. I had read about unchecking the Hardware Acceleration box and the clear media cache button--unfortunately they did not work for me.
In the meantime I also came across the 32bit/64bit discussion in this forum and learned that PE14-64bit can only be installed on Win64, while PE14-32bit can only be installed/used on Win32. (I tried to install PE14-32bit on my Win10-64bit, which failed; on the other hand, PE11-32bit worked fine on my previous Win7-64bit PC--I'm a little puzzled!)
So, unless some other option arises, I may have to try my previous PE11-32bit under my actual Win10-64bit machine. Although editing is my main goal, I am used to experimenting with all things PC.