Download Comodo Internet Security Pro 2011 Here -> one-year special installer
http://www.downloadcrew.com/article/22370-comodo_internet_security_pro_2011
Install and start Comodo 2011. Navigate to “More” -> “About” -> Serial Number -> “Copy”.
Save the serial number on your PC, you will need this serial to activate the 2012 version.
Download and Install Free Comodo Internet Security Pro 2012.
http://downloads.comodo.com/cis/download/installs/1000/standalone/cispro_installer_x86.exe
During installation, enter the serial number that you received from the 2011 version.