No, SYSTEM account would be more akin to the unix/Linux root user. There are some folders that are locked down, but it's really for security reasons. A good example is C:\Windows\CSC This is used for offline file cache and branchcache. CSC stands for Client Side Cache. Windows uses the DAC permission model (Discretionary Access Control) and even if you don't have any permissions you can, as an administrator, take ownership of almost anything and then grant yourself access. The Trusted Installer user is a special virtual user used to protect system resources and certain registry information. You can't log in with this account.