So after my rush home after my midnight purchase, I was disheartened when the Installer.exe fired up and stalled out. I feared I had a bad copy... With some experiements, I found a possible cause and thought I'd share in case anybody else runs into the same.
I'm using Windows XP Professional which is joined to a domain. The installer would not run under any of the domain usernames even though 'Authenticated Users' is in the local Administrator's group. I had to log in using a machine local user account with admin rights to get Installer.exe to do anything useful.
Hope that helps somebody.