Where is AutoCAD 2013 after you install one of the Product or Factory Design Suites?
If you want to run AutoCAD 2013 instead of AutoCAD Mechanical 2013 you won't find it on your desktop as a shortcut. It isn't added to the desktop by default.
Look in the Windows Start Menu for the AutoCAD 2013 shortcut in the AutoCAD Mechanical 2013 folder:
Right-click on AutoCAD 2013-English and choose Send To > Desktop.
Now you've got the AutoCAD 2013 shortcut on the Desktop.
This runs AutoCAD Mechanical with the <<Vanilla>> profile which is the equivalent to running AutoCAD.
You can also copy the existing AutoCAD Mechanical 2013 shortcut that's on the Desktop and replace <<ACADMPP>> with <<VANILLA>>in the Target field.