Many a times, Windows Uninstall (Add-Remove) Programs applet proves insufficient for un-installing AntiVirus or Security Suite installations, as a result of which they leave unwanted remnants on your PC. This often then causes problems esp when you go on to install another security program. Its thus always advisable to use the Removal Tools or Uninstallers for anti virus software.
Here is a list of AntiVirus Uninstallers:
Avast : Use their uninstallation utility aswClear.
AVG : AVG Uninstaller.
Avira : Avira AntiVir Registry Cleaner Tool will help you clean up all the registry entries left by this anti-virus software after the uninstallation.
CA Internet Security : Knowledge document and uninstaller.
F-Secure : Un-installation support and tool.
G DATA : Download and use the G Data removal tool AVKCleaner2009.
Kaspersky : KAVRemover is free utility that helps you to completely remove all Kaspersky Labs products. Download KAVRemove. Also visit Support.
McAfee : The McAfee Consumer Product Removal tool (MCPR.exe) removes all 2005, 2006, 2007, 2008, & 2009 versions of McAfee products. This option should be used, only after you remove your McAfee product through Uninstall Programs.
Malwarebytes: MBAM Cleaner.
NOD32 : To remove NOD32 antivirus from your Windows, simply click on the NOD32 Removal Tool, click Yes, & wait for the removal confirmation.
Panda : Panda Uninstaller.
Quick Heal : Uninstaller.
Symantec (Norton) : Use Norton Removal Tool.
Vipre AntiVirus : VP Cleaner.
ZoneAlarm: ZoneAlarm Uninstallers.
If I am missing something, please let me know.