Windows Vista introduces "user account control" (UAC) that might cause problems for some applications due to "least-privileged user accounts." Aaron Margosis released a tool, LUA Buglight, that  that might help you discover such problems. Margosis writes that the tool "is designed to help both developers and IT Pros (sysadmins) identify the specific causes of LUA bugs in desktop applications running on Windows XP, Windows Server 2003, or Windows Vista."  You can read about it and download a copy at his blog.