These are all futile efforts at hiding workplace surfing.
Many corporate offices use in house proxy servers (which cache most everything anyway)

One word: Cameras.

If you do not have admin rights you may not be able to install Firefox (or ther apps)

If you are using I.E. you are already screwed. Microsoft in their infinite wisdom saw fit to create a local system database that is locked and cannot be deleted easily. (us I.T. gods know how but it is still difficult) This file is called index .dat

Here's a free app that will allow you to do that easily-
http://www.systenance.com/indexdat.php

Remember if you are working for the man, he owns you while there. Save your surifing for home where it should be.

Thats good advice I.T. guy.
b.s.