To delete an unknown account, you must prevent the object from inheriting permissions.

Delete unknown account, you must block Object Inheritance permissions today just reinstalled server, configuration site encountered permission issues, a few more unknown accounts, account name is "unknown account (S-1-5-21-682003330-2139871995-725345543-500) ". Very eye-catching. As a result, the error message [because unknown account (S-1-5-21-682003330-2139871995-725345543-500) "inherits permissions from its parent, you cannot delete this object. To delete the unknown account (S-1-5-21-682003330-2139871995-725345543-500), you must block the object from inheriting permissions. Turn off the permission inheritance option and try to delete unknown account (S-1-5-21-682003330-2139871995-725345543-500 )".]

Solution: Click the Advanced button in the security label. Click "Administrators" under the name and remove the following "permission items that can be applied to sub-objects from the parent item, including those explicitly defined here (I).", In the displayed dialog box, click Copy. Click unknown accounts (S-1-5-21-682003330-2139871995-725345543-500), and then click the delete button below to delete these eye-catching unknown accounts. Then confirm all the way. You can easily delete an unknown account.

If you have multiple unknown accounts, repeat the preceding steps to delete them all.