Excel & Word Wont Open:filename Is Unavailable?

When I open an Excel file I get the response "Unable to read file." I can open excel itself, but just no files. old or new.When I open Word it says "The file filename is unavailable" Then when I close it, it is telling me that "The file normal already exists. do you want to replace it?" if i click yes it goes away but still wont open my file next time. If i click no it tries to save in to the TEMPLATES FILE under NORMAL. My Norton Antivirus has also taken away my privileges so I can edit the updates and Norton Internet Security says that the file cannot be found when I click on the desktop icon. The Norton Internet Security icon has disappeared off my task bar. I've been trying to download updates for windows, but it wont alow me too