What version do you have? If Win98:
It can be accessed by choosing "Tools" from the menu at the top of the browser. Then choose "Internet Options" and then click on the "Content" tab. After that click the "Enable" button to configure the browser based on content in four categories: Violence, Nudity, Sex and Language.
When these are set, the browser will prompt the Web surfer to enter a password when a questionable page is detected.
If you lose the password, there's no getting around the problem except with a little computer surgery. You're going to have to cut into the bowels of Windows to fix it. This can be a little scary, but it's quite straightforward.