John, if installation started, it shouldn't have halted like this, IUSR permissions are correct. now I am assuming you must have left something in PHP settings particularly for IIS, as Apache's and IIS's are different.
These are the settings I use to initialize PHP forMoodle
error_log="C:\php\php56\temp\"
upload_tmp_dir="C:\php\php56\temp\"
session.save_path="C:\php\php56\temp\"
cgi.force_redirect=0
cgi.fix_pathinfo=1
fastcgi.impersonate=1
fastcgi.logging=0
max_execution_time=300
date.timezone=Europe/London
input_max_vars = 2000
extension_dir= "C:\php\php56\ext\"
Rather than getting frustrated, give sometime and follow video, you may be missing something.