Update Release 3 is not a full install; rather it is using service pack technology similar to AutoCAD®- based products. Prior to installing the Update Release 3, please verify that you have already installed the First Customer Ship build of Autodesk Revit 2013 (Build: 20120221_2030) or any of the Update Releases for Autodesk Revit 2013 (Update Release 1 Build: 20120716_1115 or Update Release 2 Build: 20121003_2115).
You can apply this update to Autodesk Revit 2013 running on all supported operating systems and languages. Consult the readme file for installation instructions and be sure to install the correct update (32-bit or 64-bit) for your software and operating system. Consult the enhancements documentation for areas improved by the Update Release.
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=21891257&linkID=21208796
Source: Autodesk Site
