We have been getting numerous cases with AutoCAD product not installing.....
This issue manifests as an error in the install log when installing AutoCAD MEP 2013 or AutoCAD Structural Detailing 2013 either as part of a Suite install that includes AutoCAD 2013 or an install on a system that already has AutoCAD 2013 on it.
Executing op: CustomActionSchedule(Action=NgenCreate,ActionType=1025,Source=BinaryData,Target=NgenCreate,CustomActionData=C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Ngen.exe;;C:\Program Files\Autodesk\AutoCAD 2013\acad.exe)
Invoking remote custom action. DLL: C:\Windows\Installer\MSI5466.tmp, Entrypoint: NgenCreate
CustomAction NgenCreate returned actual error code 1603 (note this may not be 100% accurate if translation happened inside sandbox)
The root cause is a failure from ngen.exe taking action on a DLL on AutoCAD 2013 after it has been modified by the AutoCAD 2013 Service Pack 1.1.
To work around the issue, your installation of AutoCAD product must be done with an unpatched version of AutoCAD 2013. If you are installing from a Suite, you must configure AutoCAD 2013 and choose the option to not include any Service Pack(s).
If your AutoCAD 2013 is already installed, you will need to uninstall the Service Pack 1.1. In Windows 7, go to the Programs and Features control panel and click on View installed updates on the left side in order to view and uninstall the Service Pack.
Once the Service Pack 1.1 has been uninstalled, any other AutoCAD family of products should be able to be installed on the computer.
Thanks to Jeff Asbury and Alison Gangler for assistance on this post.