I meant to add that before I did the above I used the 'Everything' app to search for the 'Previews.LRDATA' but found nothing in the whole of the C Drive or D drive.
UPDATE FROM LIONEL1536:
I logged in as administrator and moved the Lightroom Catalog from my C drive to my D drive. I also changed some of the access permissions. I was then able to open LRC and import the photos I want to work on. Then I logged in as myself and was able to open LRC. I have no idea why LRC couldn't make changes to my C drive. However, I worked around that by moving the catalog file to the D drive. Now I just have to learn how to use the software.
Thanks again for your suggestions.
Lionel