I have a paid license bought in March for the PRO Version and somehow it has been removed from my computer. How to I reinstall it, I have the Key Code?

Search your computer for the installer file Ad-AwareAE.exe (size ~33 mb). If you didn't keep the installer, download the free version from here. After installation and registration with your key code, it should upgrade to Pro. Otherwise, contact Lavasoft Customer Support via the link in my signature.