I don't think you will be able to install any commercial anti virus software easily at this point, the infection will stop it.
First download Combofix from Here
to you desktop but do not run it yet.
Second download Malwarebytes from Here
to your desktop but do not run it yet.
Shut down all other programs and then run combofix you saved to your desktop, following the prompts, if needed to shut down any active anti virus program. Combofix might have to restart your system if so this will be automatic, once combofix is finished it will produce a log please post this log in your reply.
Now run Malwarebytes from your desktop, after the install select to update and run, after the update select "Full Scan". Again once it has finished it will also produce a log please post this log and the combofix log in you reply.