To create the new custom install package

• In the Symantec Endpoint Protection Manager Console, on the Admin tab, under Tasks, click Install Packages.
  The current default client installation packages appear on the right.
• Under View Install Packages, click Client Install Packages.
• Under Tasks, click Export client install package.
• Browse to or create a preferred export folder, and select it.
• Select whether or not you want to create a single ".exe" file. (Here, we need to uncheck the box to create a non .exe or a .msi package )
  
  

• Select Installation Settings and Features.
• Select Custom Install Settings from the settings drop-down.
• Select Custom feature set from the features drop-down.
• Select the group to which the client will be installed. If no group has been created, select the Default group.
• Select the Preferred Mode. The default is Computer mode.
• Click OK.
• The new install package is created in the location that you specified.
  
  

Note: SEP64.msi Package is very useful in many issues where Customers often face issues like "The Windows Installer service could not be accessed".