Also, there are a number of user files to which access is denied but I am the only user and, I assume, administrator.
Errrrrr no, the UAC will assume, unless you've told it differently, you are not the administrator,
To run windows explorer as administrator right click on the task bar icon then right click on 'windows explorer' and left click on 'run as administrator'
You may also need to open 'folder options>view (in the control panel) and tick the 'show hidden files and folders option.