Frankly, I gave up trying to install MC20. I had followed all the suggestions in the anti-virus thread but none of them worked. But recently I upgraded to Windows 10, and decided to try again. I got the same error message, so I enlisted the help of my son, who runs the IT department at a local hospital. This is what he tried:
He removed all installed versions of media center
He ran ccleaner to clean files and the registry
He disabled the windows firewall completely during installation
He manually created the install folder on D: and gave “users” full rights
None of that worked. What finally did work was installing it on the C: drive. I had been avoiding doing this because my C: drive is an SSD with only 128GB, and even before upgrading to Windows 10 it was nearly full. The SSD is for the operating system and I try to keep all programs on D:, which has plenty of room. Some programs don't give you the option to specify which drive you want it installed on. Media Center did let me specify the drive, but apparently didn't like it.