In previous versions of Windows, independent software vendors (ISVs) may have elected to place programs in the user logon path to ensure that they run each time a user logs on. While this solution may be convenient, it often results in application compatibility problems when the user is not an administrator. In addition, research also shows that a growing number of enterprise customers want to deploy their desktops as standard user. This poses a growing problem for applications that require administrator privilege to run in the user logon path, not only on Windows Vista, but also on previous version of Windows. These applications will fail to run and make configuration and administration more difficult. When a user logs on, applications that require elevated privileges, and are in the user logon path, require a full administrator access token. As a result, the user is displayed a User Account Control dialog box either requesting approval or credentials. To compound the problem, the user has no way to tie the elevation request to a specific application. To avoid this poor user experience, Windows Vista blocks applications that require elevation in the user logon path.
This functionality also helps thwart malicious software that may place itself in the user logon path.