If you have Internet Explorer, open it and go to Tools (from the menu bar) and then Internet Options.
To keep it from storing the data in the first place.
While in Internet Options.
Click on the Content Tab.
Under Auto Complete there is a Settings button. Click on that.
Uncheck the box before that says Web Address.
Internet Explorer should not save anymore address you type into the address bar.
To delete what is already there.
While in Internet Options click on the General Tab.
Under BBrowsingHistory there is Delete and Settings.
Click on Delete.
There are lots of options there, if you don't like the computer to remember your username or passwords for you, just click on the Delete All, if you do want it to remember those types of things just delete the History.
Good Luck.
By the way, if you are running an older or newer version of Internet Explorer than 7. Your instructions will be a little different, but generally the same, just the names and tabs etc will be different.
If you are running some other Browser, maybe someone else will come along with helpful instructions for those.