What are those Index.dat files all over MY PC??

Note* In older versions of Win95, the Index.dat were named MM256 and MM2048.dat. Microsoft seems to have combined the two MM files to make the new Index.dat files but left them in the same folders. Essentially, the Index.dat(s) have the same function as the old MM files.

A while back as I started looking at how Windows operate, I became aware of a few files usually hidden from the ordinary user. Now I underderstand why system files have to be "protected" and NOT easily accesible, but the ones I have found don't seem to have any function at all except to keep accounting information of everything we do in Windows. Usually these are named Index.dat and there is at least 6 of them. In the older Windows version they were called MM256 and MM2048. Funny thing is, Windows denies their existence completly and the only way to see them is with some 3rd party files hunter software. I use FileFinder. This begs the question: Why the big secrecy?

First, let do a little test. Go to C:\WINDOWS\ and look at these 3 folders: Cookies, Temporary Internet files and the very funny History folder. That's funny as in puzzling, not as in "ha-ha". Open the History folder and look inside. If you clean your Internet Explorer regulary all you will see is a folder named " Today". If you DO NOT, you will see folders with the previous day's name. So far so good. Now try opening the Today folder. It will appear empty. But we know better by now that appearances can be deceiving. Using your right mouse button, click on that History file again and look for the Properties option (it should be the last one on the list). Choosing that, look at the History folder again. Hmmmm...very interesting, isn't it?...That History folder was NOT empty at all! Mine said it contained 4 (!) files and 2(!) folders and it totaled 48.2 KB - that' s 49,378 bytes!
Doing the same thing with the Temporary Internet Folder , I found out I had 7(!) files and 5 folders totalling 32.3 KB -33,170 bytes, even when Windows insisted Temporary Internet Folder was empty! My Cookies folder had a file named Index.dat and it was 16 KB or 16,384 bytes!
Using the freeware FileFinder that I found at www.download.com, I had another look at my Cookies, History and Temporary Internet Folders. Here are the results: C:\WINDOWS\COOKIES -----Index.dat 16,384 bytes, C:\WINDOWS\HISTORY\ ----desktop.ini 113 btes, C:\WINDOWS\HISTORY\History.IE5----desktop.ini 113 bytes and index.dat 32,768 C:\WINDOWS\HISTORY\History.IE5\MSHist011999060319990604 index.dat 32,768 C:\WINDOWS\Temporary Internet Files was thre most distrubing. It contained: desktop.ini; D:\internet\Temporary Internet Files\;67;06/04/99;11:07am; index.dat ; ~\Temporary Internet Files\Content.IE5;32,768;06/04/99;11:10am; desktop.ini ;~\internet\Temporary Internet Files\Content.IE5;67;06/04/99;11:07am; desktop.ini ;~\internet\Temporary Internet Files\Content.IE5\OZ4Z0HQ7;67;06/04/99;11:07am; desktop.ini ;D:\internet\Temporary Internet Files\Content.IE5\AV6C374X;67;06/04/99;11:07am; desktop.ini ;D:\internet\Temporary Internet Files\Content.IE5\PXSITGPF;67;06/04/99;11:07am; desktop.ini ;D:\internet\Temporary Internet Files\Content.IE5\45V7IK2M;67;06/04/99;11:07am;
Now I do not want to bore you with all that gibberish. You get the idea I am sure. Find, download FileFinder from www.download.com and do all the tests yourself.
To suumorize: MM.dat or Index.dat files can be found in the floowoign locations on your HD: C:\WINDOWS\History, C:\WINDOWS\Temporary Internet Files, C:\WINDOWS\Cookies.
The questions here are: 1.what those files are, 2.what they do and 3.how to get rid of them.
Lets look at what those MM files were first. The Mm256.dat and Mm2048.dat files are cache files supposetly used by Internet Explorer. Weirdly, I DO NOT use IE, but i still have them and get them EVERY time I log on to the net. When you visit a Web page, Internet Explorer assigns the Web address a unique identification number and searches the Mm256.dat and Mm2048.dat files for that identification number. If the Web page's identification number is found, the contents of the Web page are stored locally on your computer's hard disk and Internet Explorer uses the locally stored content instead of downloading the information from the Internet. If the Web page's identification number is not found, the contents of the Web page must be downloaded from the Internet. This occurs if you have not visited the Web page before, the Web page has changed, or the Web page 's identification number has expired. When the Web page's content has been downloaded to the hard disk, the Mm256.dat or Mm2048.dat file is updated with the Web page's identification number. The Mm256.dat file is used to store the identification numbers of Web pages whose Web addresses are equal to or less than 256 characters. The Mm2048.dat is used to store the identification numbers of Web pages whoseWeb addresses are between 257 and 2048 characters. They come in three "flavours" each "small", "median" and "big". There can be found in: 1. c:\windows\history (big MM256.dat and middle mm2048.dat), 2. c:\windows\cookies (small version of both), 3.another copy of inside C:\windows\temp ( mm256.dat big version), 4. c:\windows\tempor~1\cache1~2~3~4 (middle mm256.dat & huge mm2048.dat) 5.and more in c:\windows\java\hist# You'll read inside both: Client UrlCache MMF Ver 3.2 I suspect the new Index.dat files are that same MM files renamed, because they can be found in the same folders and are the same size. The ones in the History Folder contain all the data corresponding to the links you see when its opened in Windows (they effectively are the History Folder). The ones in the Temporary Internet Files Folder contain the mapping that associates files to actual web-page elements in the cache. A cursory look at the contents of those in the Cookies folder show they contain references to at least some (if not all) the cookies set in the browser Allegedly these files collect the user's entire URL history (i.e. a record of everywhere you've ever surfed) and/or the complete summary of the directory structure hard drive. of your hard drive. By now you should have guessed that MM256.dat works together with the Cookies folder, and MM2048.dat, instead, for web-pages) I thought that by refusing to use Intrenet Explorer and using Netscape only I would be safer. They don't seem to get URL's from netscape, so I'm not sure why they're there. If I delete them they come back again.

To conclude: Microsoft's Windows95, 98, NT maintains a minimum of 12 "user activity" databases. These files are known as MM256.dat and MM2048.dat and/or Index.dat and one of each is kept in your history folder (hidden completely), your cookies folders and in each of your four cache folders (also hidden). The cookies and cache folders are not the only records MSIE keeps on your internet activities. If you use MSInternet Explorer for mail and news, everything you read and see is also recorded intact in other databases within MSInternet Explorer. A good deal of information is also stored in the registry where your file system cannot get at it. What is the reason of the 'secretness' surrounding these files is anybody guess.

The next good question I hope you are asking yourself by now is how to get rid of all those Index.dat, Mm256.dat MM2048.dat, or if it is even possible to do that. Well, there are several ways:

  • 1. Restart the PC again in MS-DOS mode and navigate via the command line to the above mentioned directories from the "C:\" prompt via the "cd" command as in "cd windows", then "cd history" and once you are there type del *.dat this deletes all of the files with the *.dat extension ie mm256.dat etc. It's true they re-generate every time you browse, but only in their most basic form of about 8192 bytes and if you read those, you don't see very much!

  • 2. Make a new folder in your auxilory drive, for example the Iomega zip drive. I named mine internet Do not make any of the 4 hidden sub-directories though. Open your browser and direct it to send use the 'Move Folder' button to point to this new directory. Delete the default directory that came with the browser and restart your computer. When you open MsIE after restarting Windows it will create 4 hidden directories, 8 mm2*.dat files and 1 hidden*.ini file. Each sub-directory will contain the 2 mm2*.dat MsIE's cache will still work the same and you can still see and recall the stored data it contains UNTIL you poke the 'Empty Folder' button.

  • 3. Read the chapter Making a Virtual Drive in Your RAM and by following the directions, you can at least get rid of the Index.dat and MMfiles generated inside the C:\Temporary Internet Files folder. You can also move your Browser's cache folders in your Virtual drive too. 1. For Netscape go to Edit, Preferences, Advanced (twice), then choose the Cache option and in the Disk Cache Folder change the dir to point to your virtual drive. if the drivce letter is D: put D:\Internet. 2. For Internet Explorer 5.0 go to Tools, Internet Options, choose the General folder, look for the Temporary Internet File option and click on the Settings button. Inside, click on the Move Folder button and direct the PC toward the same D:\Internet folder. For internet Explorer 4 go to View and then InternetOptions. In Temporary Internet you click settings. There you click move map, and after you do, you can point the location where the map has to be.

    Here are some collected questions and answers about those Indes.dat fiels and what people are saying they do, to get rid of them. Hope the info is useful to you.

    I was somewhat alamed the other day when I read something about "mm2048.dat" and "mm256.dat" files not being erased by either Window Washer or BCWipe exe.'s. I'm not the most informed when it comes to working on pc's. Could someone please enlighten me on these files: WHAT are these files? CAN they be erased (I heard it is difficult to do)? CAN (will) you explain the process to do so (if it exists)? I have to leave the board for awhile, so please, someone, if an answer is posted, please try to keep it on-line for awile until I get back and can respond. Thank you. Sorry for the long post, but these are security matters for all. Thank you.
    The files you refer to mm2048.dat and mm256.dat are usually found in c:\windows\cookies
    These are cookie files and effectively track the URL's that you have been visiting! They relate to IE3 or 4, not Netscape! You can delete them and the easiest way to do it is, when you have finished surfing and closed down your browser. Restart the PC again in MS-DOS and navigate via the command line to those directories ie from the C:\ prompt cd c:\windows\cookies this takes you to the c:\windows\cookies dir and once you are there type del *.dat this deletes all of the files with the *.dat extension ie mm256.dat etc

    Sometimes you can delete them from within windows, and other times you can not! I am not exactly sure, but I think the cookie files in the cookies dir are the 'safest' If you want to read the contents of any cookie file, go to the directory and select one of these files, (its better to use winfile for this and make sure that file manager is set to show hidden files or all files or whatever. Copy the file for example as 1.rtf(rich text format) and double click on it.

    Wordpad opens it and you can read it so if you've been to any sensitive sites, you can see them. Then just delete the larger files found in the temporary internet folder cache1 - cache4 dir's. It's true they re-generate every time you browse, but only in their most basic form of about 8192 bytes and if you read those, you don't see very much! The best thing to do is to disable cookies, or always refuse them unless you have a counter and it needs you to enable them.

    I leave my cookies 2 x 8192 bytes in the cookies folder, but delete all of the others every time that I surf. At the C:| dos prompt you can type dir mm256.dat /s and that will find every mm256.dat file on your HD do the same for the other file too.

    Answer 2:
    If you want to know how to delete those file using DOS then read my post further down this board. It tells you EXACTLY how to do it! scat CAN'T tell you how to do it using batch files because if you read his post, it states that after running the batch file, all of the other files are gone but the mm2048.dat and mm256.dat files are still there! Besides why should you need to use a seperate program to autimate something as simple as (in DOS) del *.dat That's all you need to type, to get rid of those files and if you type dir mm256.dat /s from the c:\ prompt in an MS-DOS box in windows or in DOS alone that will tell you where all of those files are on your hard drive. Do the same for the other file dir mm2048.dat /s If you are using Netscape and not MS internet explorer then the mm256.dat and mm2048.dat files will not apply because they are indigenous to internet explorer! Charlie


    The mm.dat files can be easily deleted in Explorer. However, if Windows does not allow you to delete them, then it is because they are in active use. Close all Internet applications (Netscape or I E, Eudora, PointCast, etc.) then delete the files in the normal manner. Remember that the mm.dat files are re-generated every time that you startup. So they must be deleted again after each time you surf to sites that you do not want recorded on your system. I don't know how to get rid of then permanently - maybe some other members have or will find out and let us know.

    to find mm.dat files, go to Find and enter mm* they will show up in window. Highlight the mm2048.dat or mm256.dat and from the 'File' drop down menu select 'open containing folder' for each ofthe files. You can then change the file extention to .txt and view them with word pad or note pad. You can delete them and they will be recreated on restart as empty files, as ziggy has said below.

    keep it clean and surf safe. CHARLIE:
    If you go to the scatbats url, and read it, you will see that it sats "windows will create new, 'empty' ones". These are system files. They are needed. I challenge you to try this yourself. If you are using MIE, you will see how easy it is. As for Nutscape, I don't use it. but if you know where the files are that you want deleted, you can make your own custom batch file to delete these. I can make a batch file that will completely erase, overwrite, UNformat, reformat, and restore windows to my hard drive. I've done this TWICE. So don't be trying to mislead these newbies. try it yourself. BATCH WORKS !
    As usuall, I welcome any suggestions, tips, remarqs, ets when it comes to complex subjects like the indes.dat files.