This is what happens...
I downloaded the install file, and it's called Media Center 13 and it's file type is 7z Setup SFX. It's basically a setup.exe which launches Install Wizard.
It extracts a bunch of files with a progress bar showing the % complete.
Then it gives me a license agreement that I can accept or decline. I accept it (without reading, like everyone else).
I choose Custom (for the portable install) and click Next.
Then it wants the "Destination Directory". It gives me an "Install To" prompt with an option to choose a directory. I choose J:\MediaCenter on my portable drive. The registration file is also in that same directory.
I click Next and I get the message "Failure Copying License: Install Wizard can only perform a portable install if you have a valid license on this machine." My only option is to click OK. I get another summary message telling me to reboot or whatever, and the software exits.