Absolutely. As great as Windows Xp is, hackers love to find its holes. An Anti Virus For Windows XP will ensure those holes are filled and those terrible viruses cannot infect your computer. Viruses can do many things including slowing down the computer so that it is useless. Viruses can aslo use your email and address book to spread the virus to others. So as dangerous as your computer getting effect by a virus is, a much worse scenerio is its capability to use your reputation to spread to the rest of your friends. You simply must have an anti-virus application running.