50 people all use same computer. Windows XP.all have different email and what settings are best for web?

All use same computer...Windows XP Pro...all have different email through Yahoo and surf the web...what are the right settings so that they can take surveys on the same computer but not be mistaken for same person since its 1 computer would that be "cookie" settings or Security settings? Right now a person takes a survey and its says they completed it already but they have not...the computer never did that before...what adjustment has changed to make that happen? What do you adjust under internet options? Advanced settings to allow every person to use the same computer via email address? Thanks

50 people all use same computer. Windows XP.all have different email and what settings are best for web?
You can actually clear all the cookies and temporary internet files (including offline) but it's not only that, it will also depend on the website where you took the survey. Some websites will also check on the your IP address if that current address have already log to there server. If the server knows that you have log, then you can no longer take the same survey in a certain period of time. :-)