Running multiple antivirus products on the same computer may degrade performance and cause system instability because the high usage of the memory of those programs. Each antivirus program need to run on the background and monitor the process which is running on the computer for a real time protection. From my experience better is to have only one Antivirus product at a time for the protection.
Some time removal of antivirus program may complex task because of the inbuilt protection within the program itself. Here I would like to share the removal tools for common antivirus software. Click the link associated with the antivirus software currently installed on your system and follow the prompts or instructions on the website to remove the antivirus.
Avast http://files.avast.com/files/eng/aswclear.exe
AVG http://www.avg.com/us-en/utilities
BitDefender http://www.bitdefender.com/uninstall
Kaspersky http://support.kaspersky.com/downloads/utils/kavremover.exe
McAfee http://download.mcafee.com/products/licensed/cust_support_patches/MCPR.exe
Norton ftp://ftp.symantec.com/public/english_us_canada/removal_tools/Norton_Removal_Tool.exe
Windows Live OneCare http://download.microsoft.com/download/4/c/b/4cb845e7-1076-437b-852a-7842a8ab13c8/OneCareCleanUp.exe
Windows Security Essentials http://support.microsoft.com/kb/2435760
Zone Alarm http://download.zonealarm.com/bin/free/support/download/clean.exe
Note: removing antivirus software will remove the settings which you saved on Antivirus program such as firewall, identity safe etc…