Index.dat files are used by Internet Explorer and Windows to store history, Internet cache, cookies, UserData records and other information about what you have done in Internet or in your PC. Although some of their functions are useful, they are dangerous privacy threat - any person with even little knowledge about index.dat files locations and structure can see history of almost all of your computer activities. Index.dat files are not the only privacy threat but they are the most obscure and dangerous one because they are hard to find and even harder to delete.Note: these things aren't necessarily problems in and of themselves, so if you're not experiencing random crashes, don't waste your time solving problems that aren't there.According to Microsoft, these files are used to cache visited Web sites to help speed up the loading of Web pages in Internet Explorer. Obviously this cannot be the case because when you clear the Temporary Internet Files the "index.dat" files remain behind and continue to grow. If you delete or clear the Temporary Internet Files, there is absolutely no need to index the URL cache because those files no longer exist. PC cleaning is always a good idea to keep your computer running stably.
Where are index.dat files located?
The location of index.dat files depends on the version of Windows and whether or not you are using user profiles. Regardless of Windows version in many cases you can't see or find index.dat file using Windows Explorer. There is a little file called desktop.ini in each directory where index.dat file is located. This desktop.ini file forces Windows Explorer to hide index.dat files and to show the contents of Internet cache or history instead. However you can use some other file utility and binary (hex) editor to find the files and read their content. If you have Windows Vita then index.dat files are in these locations (note that on your PC they can be on other drive instead of drive C).
How to delete index.dat file manually?
The index.dat file are used by Internet Explorer and Windows Explorer. You cannot delete a file that is in use by a running program. If you feel you need to delete the file, you will have to shutdown all instances of Explorer and IE. This includes applications that may host the Webbrowser control: Outlook, Messenger, IE, Product Studio, Visual Studio, Help, Windows Media Player, etc. Your best bet is just close everything. When you are left with a desktop and a start menu, you will still need to shutdown Explorer. To cleanly shutdown Explorer: Start->Shutdown->CTRL+ALT+SHIFT+Click 'Cancel'. You can use Task Manager (CTRL+SHIFT+ESC, File->Run...) at this point to open a command window. You should be able to go delete the index.dat file.
For more details, please visit index.dat removal instruction.
Note: Windows Optimization is a dangerous job which might lead to system crash. You're on risk of your own.
