When you download the bootinfoscript, it will be a tar.gz file: bootinfoscript-061.tar.gz. You need to extract it either by right clicking on this file and selecting one of the 'extract' options or by opening a terminal and going to wherever it downloaded, usually the user Downloads file. From there:
tar -zxvf bootinfoscript-061.tar.gz
should extract it and you should have a directory named bootinfoscript. Change to that directory and run the command you did. Posting the command including the prompt would be helpful to point out possible problems.
Installing windows 7 you would probably need to use a custom install if that's available with 7 in order to select the partition you want.