I have recently upgraded Office XP to 2007 pro plus omitting Outlook
from the upgrade by selecting 'Not Available' on the customized
install. When i have re-run the installer to add Outlook at a later
point the only option i get is to unintstall all Office products and
start from scratch.

I have also noticed that on occasions when running a full upgrade
including Outlook that the install fails and rolls back - again
prompting a full un-install of all Office packages.

trying to run just the OutlookMUI en-us.msi is also useless as this
seems to do nothing.