Most of our installers are having trouble in Vista. Among the reasons, the fact that we normally install our content under "Program Files" is something that Vista doesn't like for security reasons.
Tom has posted about this some time ago: http://blogs.msdn.com/tomholl/archive/2006/09/15/756747.aspx
To successfully install CAB on Windows Vista you must follow the following steps:
If you try to run CAB .msi without "Run as administrator" command the installation will fail.
You can't select "Run as administrator" command directly on CAB .msi file because this options is not available on Windows Installer Packages.
Same is valid on Enterprise Library and other content from us.