[eluser]Unknown[/eluser]
In case this might help someone.
I had problem installing Backend pro on my local system, with error about file/folder not being writable. Since my installation was in slightly unusual location the solution was to replace $_SERVER['DOCUMENT_ROOT'] . $_SERVER['SCRIPT_NAME'] with $_SERVER['SCRIPT_FILENAME'] in install/index.php and RUN.php. I also had to create directory cache in application folder.