index.dat

The index.dat file was introduced with Internet Explorer version 4. It is a file that contains a record of every URL you visit when using your browser, and it is incredibly difficult to delete. To the best of my ability, I have found no use for this file, and I'm a little irritated that Microsoft deems it necessary to store my browsing habits in files that they don't tell me about.

I first came across this file after upgrading to Windows ME. I was running Norton SpeedDisk and noticed several blocks of data colored red, meaning that some files contained in that cluster were unmoveable. This set off little warning bells (there had been no such red blocks reported when I was using 98, and SpeedDisk will defrag even the Windows swap file) so I did a little hunting, and came across a tedious but effective method for eliminating all traces of this file. Be warned however, that the file will be re-created, so you'll need to do this on a regular basis.

Windows 95 and Windows 98 users have it a bit easier than Windows ME users (I'm not even going to attempt to explain NT or 2k if someone else wants to do that, feel free).

For Windows 9x users, perform the following steps:

index.dat is a file that's created to store the indexing into the Temporary Internet Files directory for each cached page, and is designed to hold the history of cache expiration times. If you minimize the amount of data in your Temporary Internet Files directory (get a proxy server that always modifies the HTTP headers to 'Expires: Now' or something), it won't grow nearly so huge because it won't have anything (legitimately) in its cache.

An even better solution if you want to keep the cache as small as possible is to open the Tools - Internet Options dialog, go to the Advanced tab and check the Empty Temporary Internet Files folder when browser is closed checkbox. You can also go to the General tab and decrease the maximum size of the cache.

There is also a Delete files button on the General tab, which you can use to delete the files in the cache. index.dat itself will not be deleted or emptied. That's probably a bug, but...

Note: This applies to IE5, but should work at least in IE4 and upwards.

If you want to do a real delete under Windows NT/2000, you should log in as Administrator. If that is the account you are using to "surf", then create another account with administrator rights and log in as that instead. Then go to C:\WINNT\Profiles\username (NT 4) or C:\Documents and settings\username (2000) and find the stuff to delete. The Temporary Internet Files folder is usually in the Local Settings subdirectory.