It might be in the browser rather than the computer. If you are using mozilla firefox, it is automatically set to forget your history. Google chrome and Safari both have private browsing options you may clicked accidentally. I'm guessing internet explorer would as well but it has been forever since I've used it. These options are located in the preferences or tools bars at the top of your browser and you can tick or untick them to remember your history. Good luck :) Sorry I can't be more specific, I'm on a mac and have forgotten what PC's look like at the top so I can't check exactly what steps you should take.