For some reason I managed to only become paranoid about this file recently. I usually clean my registry, temporary files/directories, internet temporary files / histories, etc.

But the index.dat file I have never touched. Yesterday i was able to delete it by creating a new profile, but I still can't delete the index.dat files located in the systemprofile directory. Is it possible?

I have read that it's possible to delete index.dat files by closing explorer.exe and using cmd. I will try this tonight, but until then, can I get a confirmation?

Also, general questions:

- does index.dat only store cookies, search strings, histories, etc of events in internet explorer or does it include firefox as well? I use firefox mostly. I checked my index.dat file at home and it seemed grossly small considering I have been using windows for months.
- anything else I should be overtly worried about?