Index.dat files are hidden files that record information about Internet browsing history and cookies stored on your computer. Most people erroneously believe that when they delete their Internet history that it is gone forever. However, it is not, because that information is stored in the index.dat file. Since the file is hidden, most people don’t know of its existence. If you can open index.dat files, you can view previously deleted Internet history.
Open your computer’s search program by clicking on “Start” and then “Search.”
Click on “Tools” located in the menu bar at the top of the search window and select “Folder Options” from the drop-down menu that appears.
Click on “View” tab of the “Folder Options” window.
Select “Show hidden files and folders” beneath the “Hidden files and folders” subheading.
Deselect the options to “Hide extensions for known file types” and “Hide protected operating system files.” Click “OK” to save your changes.
Set your search parameters to search “All Files and Folders” and to look in the “C Drive,” and then input “index.dat” into the search bar and click “Search.”
Download and install an index.dat file reader such as Index Dat Spy (see Resources) onto your computer, then open the index.dat file within the program to read it.
Restore your default file and folder options after you are done by clicking on “Restore Defaults” located within the “View” tab of the “Folder Options” window.
Beware of not restoring your default file and folder options once you are done, for you could damage important hidden or system files if you don’t.