O = Office, E = Access Database Engine.Tried with O2013 and E2013 did't work, tried O2010 and E2013, and O2010 and same E2010, all failed. /passive option to install engine without complaining that x86 O is installed corrupted my O instalation and OS was unable to repair it. So of few tried combinations and orders only one worked, and this did not cause complaints from OS that other component is installed.