You can do a disk check with the chkdsk.exe program.
If you run the chkdsk.exe program from a cmd.exe Command window then you can read the response from the chkdsk.exe program.

Open a cmd.exe window:

Start > Run: cmd.exe <press Enter>

At the command prompt (>) type or Copy&Paste: chkdsk.exe /f /r <press Enter> (put a space before /f and /r)

If you get something like: Would you like to schedule this volume to be checked the next time the system restarts? y/n then answer the question with "Y" and close all programs and reboot the computer.

Thank you very much for your response. I solved the problem by removing the folders containing my favorites, etc., to another location. I moved the rest of the Profile folder to a different location and downloaded a newer version of firefox and added the favorites, etc, replacing those that came with the new version. Firefox works fine now.