Installing CI3 on Windows shared hosting

Hi all, I've struggled 6 hours before posting here.
I feel kinda stupid because it seems that I'm the only one in the world that can't set up a working installation of CI.
My company owns a Windows-based hosting with an existing site in it.
When I connect via FTP to the hosting I see, in the base directory, only the folder "mydomain.com"; the index.html (that's displayed when someone connects to http://www.mydomain.com) is in that folder. I can't create a directory at the same level of "mydomain.com".
Now I want to start to use CI, so I downloaded v3 and put it in ci/ subdir; if I go to http://www.mydomain.com/ci/ I see the default welcome page. So far so good.
The problems begin when I try to add some controllers... there's NO WAY to display them, the default page is always displayed, even if I enter a inexistent controller.
I've tried to change the base_url in config.php like this:
'http://www.mydomain.com/ci/'
'http://www.mydomain.com/ci'
'http://www.mydomain.com/'
I've also tried to look for the absolute path of the script via phpinfo...
'D:\inetpub\webs\mycompanycom\ci\\'
I feel VERY frustrated. The hosting company is the italian Aruba.