there is an "antivirus" ad that is so deep that it ruined the harddrive on the p.c. at work. even going thru norton/symantec and their "cure" several times, the virus continued to overwhelm the system, and eventually ruined it. even turning off the computer and stripping all the cookies didn't do the trick. one of the IT boys eventually tried a "scorched earth" approach, and couldn't fix it. it "finds" viruses on your computer, and "offers" to fix them. if you click on the "yes" button, it takes over. the one we had is called "antivirus 2010". do your best to just avoid it if you can--and the back button or a quick shutdown is the best response. (even if you pay for their antivirus sservice, it continues to eat your system. ) BEWARE!!