It is standard and if you delete it, it will return but smaller.

Try here:
http://www.mvps.org/winhelp2002/delcache.htm

...Alan

Index.dat is part of Windows TIF management system, it can be deleted from
DOS but will be immediately recreated on next boot. It is not a problem it
belongs there

Actually, at long last, I've come to like my TIFs! The others are right,
that the Index.dat there is normal & large. Anyway...

Do not delete TIFs individually, as you may cause corruption. Here is
the way...

"Control Panel, Internet Options, Delete Files button, bolt Delete all
offline content, OK, OK"

   That does a credible job, in IE6 anyway.  Note: It may take a few
moments: DON"T be impatient. The Index.dat inside Content.IE5 will
retain it's size, but is cleared or reset to emptiness. You still will
see Cookies in the main TIF folder, but all the weirdly named folders in
Content.IE5 will be gone

   These were your Temporary Internet Files, which, since V4, has an
involvement with Windows Update. It's main purpose is to hold
bits/pieces of sites you visit, to make it quicker to load next visit.
Also, it is a work area for OE6. Naturally, TIFs will grow back. It's
size is controllable by the slider & input box under the Settings
button.

If that fails to get them all, then...

Some Cookies bleed into TIFs, so... "START, Settings, Control Panel,
Internet Options, Delete Cookies button". (Note, some site specific
passwords/settings will be wiped.)

If you STILL have matter in TIFs or in Cookies after that, it is
possible you have a horrible corruption that can likely be cured with a
DOS delete...

Verify, in Windows, where these folders are located before proceeding.

 (a) "START, Find, F/F".
 (b) Enter "Cookies, Tempor~1, History" (no quotes) in "Named".
 (c) Click the "Advanced" button, & use the dropdown to select
"Folder".
 (d) Then click the "Find Now" button.
       If it is not in "C:\Windows", adjust the Deltree's below. If you
have more than one of any, then perhaps stop & report back.
 (c) "Control Panel, Internet Options, Settings button"
       Where does it say Temporary Internet Files are located? Use that
path below, but substitute "Tempor~1" for "Temporary Internet Files".

(1) "START, Shut Down, Restart in MS-DOS Mode"

(2) SMARTDRV
     This speeds up hard drive processing considerably in DOS--
considerably, & yet it may still seem slow if TIFs are incredibly huge!

(3) DELTREE  C:\Windows\Cookies\  /y
     These are your Cookies. They may hold settings & passwords, site
specific.

(4) DELTREE  C:\Windows\Tempor~1\  /y
     These are your Temporary Internet Files. A DOS delete does reset
the Index.dat in Content.IE5 to 32 KB. It won't stay that small for
long. However, Cookies in the top TIF folder would survive this Deltree.

(5) DELTREE  C:\Windows\History\  /y
     This is a collection of the sites you have visited. It will begin
to grow again, depending upon "Days to keep..." at "Internet Options,
General tab".

(6) EXIT or Ctrl-Alt-Del to Windows

WARNING: DELTREE is a powerful command. It will wipe out the folder you
specify. DO NOT HIT ENTER too soon, or you will wipe out your system.
Get all the way to the end of those DELTREE lines.