Seems to be aimed at windows 95
however its true about hidden files, but they are not as inaccessable as that.
there are many utilities that clear Content IE5 securely. if you are that concerned about security then use evidence eliminator.
Some of these hidden files are ligit and should not be deleted because they are required to keep windows functional, and anyway if you delete them windows recreates them anyway.
you only need to worry more about hackers, malware and spyware that compromise your privacy, a good firewall like Zone Alarm and good antispyware like adwareAlert will protect your privacy.