Help with redirecting issues

I recently purchased norton antivirus2010 and after its first scan it got rid of 23 threats but I am still having issues with my computer.  Whenever I am using a browser I experience the following problems:

 

  • a new tab opens with the web address of google analytics and then turns into google.com
  • when I use a search enginge the first link I always click on opens up a random webpage..usually another search engine
  • though  not as frequent as the other 2 issues, every now and then my webpage will get redirected to random sites ranging from viagra.com to porn.com