No input file specified during install

Hello! I am currently trying to install a secondary version of wordpress into the back end of the website gpsstudios.com. we all ready have an older version of wordpress installed into the webroot folder of the website with a template.
We are trying to install wordpress into a different directory (named TEST) so that way we can build a new template without affecting the current live website. I have successfully loaded all the wordpress files into the TEST directory using the FTP client Filezilla, and edited the wp-config.php file the way that our hosting (brinkster) has specified.
BUT! When I go to access the install file @ http://www.gpsstudios.com/TEST/wp-admin/install.php i get the very vague message that “no input file is specified.” is there something that I could be doing wrong?