On my newest machine, I have a fresh installation of Windows Vista Ultimate that I installed Office 2007 to. After running Outlook 2007 the first time, Office 2007 goes through a configuration step that requires a reboot, but I received this error:

Error 1719: The Windows Installer service could not be accessed

There is an updated KB entry with recommended steps to fix the problem here: http://support.microsoft.com/kb/315346/en-us

This entry doesn't mention Vista at all, and in fact, I was able to repair the problem on my Vista machine just by running the following command line instructions, in this order:

msiexec /unregister

msiexec /register

So, if you have this problem, give that a go first...then consult with the KB entry if you still have issues.