Thanks to Mess.be for spotting this - a Knowledge Base article on what to do if you can't get Windows Live apps to install.  The article lists the most common problems:

•The system does not meet the minimum requirements for the Windows Live service.
•You are trying to install the selected Windows Live service while you are logged on to the computer as a user who does not have administrator permissions.
•You have an earlier version of the Windows Live service installed.
•A file that must be overwritten is being used by another program.
•Another software application blocked the installation of the Windows Live service.
•Your installation files are missing required components.

The KB article goes on to detail how to get around Vista's User Account Control quagmire, and in addition, the article provides a link to a zip file that will uninstall Windows Live services:

WL-Beta-remove.zip

..so that one could (hopefully not give up but) start all over again.

Commentary: While these problems seem fairly benign, typical of uninformed users, the existence of this KB article seems to acknowledge that users are having problems with the Windows Live Suite - which may actually cause more problems than it solves.  Just ask the 64bit Vista users about that one.  Yes we know that a fix is promised for the 64bit issues, but with apps like Windows Live Writer and now Windows Live Photo Gallery and its connection with Flickr, does it make sense to even give the appearance of forcing users to install what will surely be considered "bloatware"?