Why do you need a track eraser?
Your computer is tracking all your activities. Anyone who can touch your computer can know the website you have visited, the web pages, images and videos you have ever seen. They will also know which files you have just opened in Office and many other applications.

All these tracks are stored in your hard disk. Just emptying the Recycle Bin and deleting the Internet cache in web browser will not protect you at all. Even your hard disk is formatted, others can know your past activities using some tools even several years later.

More info:
hxxp://www.sys-shield.com/trackeraser.htm