If its the XP 2008 antivirus, you cannot remove it. It actually imbeds and replaces some windows files. To get rid of all of it is to fry your windows installation. If thats the antivirus virus you're talking about, the only way to remove it is to format your computer.
And you don't have to click something or download something to get it. I managed to, and I never click stupid flashy banners. Just try taking the comp to a store that does repairs, they ought to be able to fix it. Or you can try at home with the recovery CDs or recovery partition, whichever one your computer has.
Formatting DOES ERASE EVERYTHING. So make sure you have some way to back up everything you like.
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Every time you think you've made it idiot proof, someone comes along and invents a better idiot.
?the end of our exploring, will be to arrive where we started, and know the place for the first time. - T.S. Eliot