MATLAB: Get the Passcode (PLP)/License File

installationr2007a

I have a DVD MATLAB R2007a, and it said that "Because you are subscribed to MathWorks Software Maintenance Service, you can now install the R2007a versions of products you are licensed to use." How can I get the PLP License File to install the R2007a MATLAB.
Thanks, Man Leung, leung_m_f@yahoo.com