I have anti virus 2005 installed but i tried to install 2007 but the computer didn't accept it&

if it's norton you have to go to google.com and type in free download of norton removal tool and download that uninstall the 2005 version run norton removal tool and install the new version bamm lol done....if it's something else then go to start %26gt;%26gt;%26gt;run%26gt;%26gt;%26gt;type in regedit ....after uninstalling the program go to any folders that well are that program and delete them and then install the new 2007 if it says that it needs windows installer go to microsoft and download it for free you didn't tell what kind of antivirus so it could be many things hope this helped though