Just mount install.wim and copy it to your mounted vista source. In audit mode, autounattend or cmd it will work. But at de end of Office installation you will get a window asking what to do, (it was not relevant 'cause I put it just before the anti-virus at the end, anyway, just click ok to go on. But first preparing Office for unattend, with custom-uA.xml is the best way. Do a search. Regards