I just got almost to the end of the installation process.
I got this text:
"
Not Acceptable
An appropriate representation of the requested resource /cgi-bin/mt/mt-upgrade.cgi could not be found on this server.
Additionally, a 404 Not Found
error was encountered while trying to use an ErrorDocument to handle the request.
"
What does this mean?
The final screen was weird. It asked me to create an url for my "first website".
I'm not trying to create a website. I already have a website. I want to add a blog.
So I put in the address of my blog. Currently there's a Wordpress blog there. Should I delete that one first (I thought it would simply overwrite it).
Thanks - comments much appreciated.
Reported on Movable Type 5

Here's another error text I got:
"Error:
406 Not Acceptable
Not Acceptable
An appropriate representation of the requested resource /cgi-bin/mt/mt-upgrade.cgi could not be found on this server.
Additionally, a 404 Not Found
error was encountered while trying to use an ErrorDocument to handle the request.
"
I have removed the Wordpress blog, but the error message is the same.
So it doesn't have to do with the Wordpress blog.
Probably it has to do with the title.
I found cgi-bin/mt/mt-upgrade.cgi
It's there in the mt folder.
Permission is set to 755.
Why does the Configuration fail my installation anyway?
Problem solved.
For some reason the mt-upgrade.cgi was being blocked by my web host's web server security module.
But they are great guys and discovered the problem in a short time.
Graciousness, this also good