If it is a Windows login script, it will not work on Mac. Since there is no DOS / Windows, you won't be able to use Windows commands to map drives and so on.
Instead, manually map any drives you want on the Mac, then drag these drives into the Startup Items panel in System Preferences --> Accounts. That way, they'll map automatically when the Mac is restarted.
If this doesn't answer your question, please give us a little more to go off. What are you trying to do with the login script?