Thank you, Steve. I spent some time on an Adobe chat to try to resolve this, and the rep did a remote session and fixed it. What I had to do was go into the Task Manager and CPU details and stop the installer process. When I had been there the Task Manager had said that it was taking up 0% so I had assumed it wasn't running. Once he closed it I was good to go.
But, embarrassingly enough, I couldn't figure out how to delete this question. If you can tell me how I can do that, unless you think the procedure that the rep used would be helpful to someone else.
Thanks again,
Carol