[modeller_usage] Problem in running script file

I have installed Modeller and python2.3 version.After making all three files (i.e.,atom,alignment and script files in a folder placed on desktop) and changing directory, when I run command i.e., mod9v8 model-default.py.http://model-default.py.it/It is showing result i.e.,'mod9v8' is not recognised as an internal and external command,operable file or batch file.Please guide me to troubleshoot this problem as soon as possible.