If you've tried installing it already, you know it doesn't work.  Rich Mercer posted the answer, which is to run the msi as an administrator.  Unfortunately, you can't just right mouse click and run as Administrator.  For details on the work around (a bat file) check out Rich's blog post about it.

UPDATE: The issue with this has been fixed in Windows Vista RC2 (5744) and you do not need the workaround anymore to get it installed.