Please see Setting Firefox as the default browser does not work - What to do

Windows Explorer is the file browser in the Windows operating system; nothing to do with Internet Explorer, which is a web browser like Firefox.

You can open image files in Firefox by using File > Open File; then what you are using to look thru your folders is Windows Explorer.

You can do a disk check with the chkdsk.exe program.

• http://support.microsoft.com/kb/315265/

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.