Thank you for responding. No, I haven't tried the actions you mentioned and I am not sure how to do them. If you'll tell me what to do, I will give it a try. The problem occurred when I first got this Dell computer; then "went away" and has now reappeared. When I did an internet search, via Ask Jeeves, another user with the same problem turned up, but no solutions were ever provided.
Anyway, I'll wait for your advice. And, again, thank you.