what is a cookie and how can it affect my computer?
Cookies are used for storing information about you or your preferences. For instance, cookies let TechSpot know who you are, so you don't have to log in every time you come here. Look at this page, at CookieCentral.com. It pretty much explains what cookies are.
Some programs, like Zone Alarm Pro, (a firewall), let you block certain cookies if you don't want them on your computer. Also, I use MyIE2 as my browser, and you can configure it to clear ALL cookies when you shut it down if you want. But if you do that you will have to log in to every site that you have personalized, like MyYahoo.com or any site that you have to log in.