Option 1: Put the script in the "startup" folder so it runs automatically when the PC is rebooted.
Option 2: Set the value of the optional parameter named 'bUpdateProfile" to true, so that the mapping will persist with the user. (This is how it is in Windows anyway. If I log onto a PC, the mapped drives/printers, etc may be different than if you log on to it.)
See this article for an explanation of the bUpdateProfile parameter (as well as usage of the MapNetworkDrive function in general):
http://msdn.microsoft.com/en-us/library/8kst88h6(VS.85).aspx