Screwing up a computer isn't the right term maybe. But when I bought my first PC it had Norton installed ( with a lot of other things one doesn't need) when I wanted to update Norton by installing the new bought Norton antivrus I had to remove the old stuff. It never did unless I wanted to end up with a computer that did not start. So I had no antivirus at all till the motherboard went up in smoke and I bought a new motherboard and cleaned out the harddisk completely, then I bought and installed McAfee. Norton prevents viri having control of your PC, but also prevents me having control it looks... thank you very much.