Problems can't uninstall an antivirus program can be due to different reasons. To overcome this problem, it could be done manually by deleting all files and remove the registry settings of the antivirus program . Besides this way, can also be done with a more simple way that's to use antivirus program removal tool.
A removal-tool is an utility used to detect and remove specific viruses,This is not a substitute for full antivirus protection, but a tool to assist administrators or users when dealing with an infected system
And the best Action antivirus removal tool [free version] that I recommend from avira products :