Windows controls access to resources with Access Control Lists (ACLs). An ACL specifically grants access to a user or to a group. Privileges are additive, meaning that users have the highest access given to their account and to any groups to which they belong. The exception is No Access, which overrides any other privileges.
The group Everyone contains every account on the system. Using this group is a handy way to set privileges, but can be a risky way to deny them. If a file or directory has No Access for Everyone, it will be unusable until someone (such as the Administrator) takes ownership and resets the privileges.
File permissions are set by the account that owns the file. To override permissions, a non-owner must have the Take Ownership privilege and use it to take ownership of the file before setting permissions.
Setting file permissions requires Administrator privileges. The topics in this help section list some key considerations for performing this activity. For specific instructions, consult your operating system documentation.