Hello,
The Symantec Endpoint Protection Installation packages are not seperate for Windows XP and Windows 7 machines.
However, make sure that you carry the Latest version of SEP on your machines, so that they are supported for your Operating System.
About Maintaining Consistency of Software Versions throughout a SEP 11 Organization
http://www.symantec.com/docs/TECH131660
How to create new client installation packages in the Symantec Endpoint Protection Manager console
http://www.symantec.com/docs/TECH102215
Creating custom client installation packages in the Symantec Endpoint Protection Manager console
http://www.symantec.com/docs/TECH102817
Hope that helps!!