Free antivirus! Microsoft Security Essentials is… pretty good.

I don't care who you are, free is good.  Microsoft has made a decent antivirus program available for free to all legitimate owners of Windows XP, Windows Vista, or Windows 7.  It is called Microsoft Security Essentials.

http://www.microsoft.com/security_essentials/

It isn't the best, but hey, it is free!  Cnet.com gave it decent reviews as have several other antivirus rating sites.  Here is an article from cnet.com.

http://news.cnet.com/8301-1009_3-10366232-83.html

If you download it, make sure you save it, then run the installer.  Don't just click run after you click the download link.  After it is installed and has done it's automatic updating, remove any previous antivirus or antimalware software you might have.  Get rid of any antispyware software too.