The index.dat file is constantly used by Internet Explorer to store information needed to display web pages and other information online. It can also store log in information and other personal details.  This file is used constantly by Windows, so SparkTrust Privacy Cleaner is unable to remove it as part of a normal scan.  When SparkTrust Privacy Cleaner prompts you to restart your computer it deletes this file while it is not in use and as your computer boots it will create a new copy of index.dat.

As you use your computer this new copy of index.dat will gather information, so we suggest removing it regularly to protect your personal details.