The system account and the administrator account (Administrators group) have the same file privileges, but they have different functions. The system account is used by the operating system and by services that run under Windows. For example, defragment applications use the system account to access the hard disks. There are many other services and processes within Windows that need the capability to log on internally (for example during a Windows installation). The system account was designed for that purpose; it is an internal account, does not show up in User Manager, cannot be added to any groups, and cannot have user rights assigned to it. On the other hand, the system account does show up on an NTFS volume in File Manager in the Permissions portion of the Security menu. By default, the system account is granted full control to all files on an NTFS volume. Here the system account has the same functional privileges as the administrator account. In other words, it is impossible to login with the System Account. As the word speak for itself, SYSTEM Account is used by the system and it's not intended to be used as a user account. If you can't delete some keys in the registry when logged as an administrator, there's probably a good reason for it. But if you still wan't to delete those files, right click on the file in registry and grant the modify/full permission to admin group.