Completely Remove Your Anti-Virus Software

Running two antivirus programs and security suites the same computer can cause system instability and degraded performance. It is important that any previously installed antivirus programs and security suites are uninstalled from your system before installing a new one.

A typical uninstallation using the Windows removal tool (Add/Remove Programs) is often insufficient, removal tools.
For the most common programs the removal tools can be downloaded from the following:

Avast:
http://files.avast.com/files/eng/aswclear.exe

AVG:
www.avg.com/download-tools

BitDefender:
http://kb.bitdefender.com/KB333-en--How-to-uninstall-BitDefender.html

CA:
http://homeofficekb.ca.com/CIDocument.asp?KDId=3125&Preview=0&Return=0&GUID=DF325E0AA0AB4264AF47E4BEA49F571B

F-Secure:
http://support.f-secure.com/enu/corporate/downloads/removeav.shtml

Kaspersky:
http://usa.kaspersky.com/support/home-support.php?selected_faq_id=193239348&selected_product_id=176492845&selected_topic_id=176492916

McAfee:
http://download.mcafee.com/products/licensed/cust_support_patches/MCPR.exe

Panda:
http://www.pandasecurity.com/resources/sop/UNINSTALLER_08.exe

Symantec (Norton):
http://solutions.symantec.com/sdccommon/asp/symcu...

Trend Micro:
http://esupport.trendmicro.com/support/viewxml.do?ContentID=EN-1033129