BleepingComputer.com: Account Unknown in security tab?

I reformatted this computer recently and backed it up using the special HP backup program in the BIOS. Anyway I just noticed that alot of the files have a new icon next to them that i don't recognize... it looks like this:


and when I right click it > Properties > Security i see this:


Any ideas what this "Account Unknown" thing is?

The S-1-5-21-... is known as a "security identifier" or SID. This is an internal identifier of User Accounts. You are seeing this because there are still remnants of the old account still in the Registry. You will be better to create a new account, and secure the proper privileges. This ID will stick in there, and will not be removed. The Windows System does not go through and delete all the information as the account is deleted. The system can no longer access the SID, because the Account no longer exists.

The REASON for this issue is that the SYSTEM was not able to connect to a domain controller to help delete the proper information.

The RESOLUTION for this issue is to leave the SID alone and Set up a new account and enable the proper permissions.