ah yes, the fine print... lol
Follow these bits of advice from Engel and you should be alright:
Windows Installer 3.1 v2 (3.1.4000.2435) is availªble
http://support.microsoft.com/kb/893803
Whatever you do, (installing and updateting or unistalling) always as a
adinistratºr.
This is the key!
Can you gº to Windows Update, select Express (Get high-priority updates),
and apply all offered updªtes
http://update.microsoft.com
Once that is finished, can you verify the update installs? There are many
pre-requisite files which are needed from windows update and signature
update
with windows defender will fail until you hªve these files.