Install XAMPP, install latest MyBB version and disable "Friendly Redirection Pages" in ACP. After this, logging in will fail and you will be redirected to http://localhost/forum/http://localhost/forum/index.php. This happens since MyBB version 1.8.8.
This was posted here.
A proposal for fixing this issue can be found here.
This was posted here.
A proposal for fixing this issue can be found here.