"Install an antivirus even though a malware blocks it."
With Malwarebytes Chameleon you'll be absolutely sure that no malicious software can prevent you installing and running the antivirus program from this same company, Malwarebytes Anti Malware, even if your PC is infected and access to such programs is blocked.
For this simple free tool is designed to download and install directly on your PC, the antivirus Malwarebytes Anti Malware, even if such programs are blocked. Malwarebytes Chameleon "dodges" those programs, and through the command line installation, before they realize, Malwarebytes Anti Malware is installed on your PC, and ready to remove them! Kill everything, and you can then safely install another antivirus on your PC, or stay with the antivirus already installed by Malwarebytes Chameleon. You decide.