What does [298] SQLServer Error: 15404, Could not obtain information about Windows NT group/user 'WIN-443PT0LULQU\Administrator', error code 0x534

I'm going slightly nuts. I'm a programmer by trade - and I only dabble in NT security and DB setup issues. However, we had a server fail to reboot after a MS Update. I've restored the entire machine from Windows Backup - but I've realized that I cannot rebuild the machine because one cannot realistically use a Windows Backup to restore a database to a different machine, AFAICT. Rather, I need actual DB backups to do that. In pursuit of having regular SQL Server backups, I'm running into the title error: SQLServer Error: 15404, Could not obtain information about Windows NT group/user 'WIN-443PT0LULQU\Administrator', error code 0x534 Essentially, I've enabled SQL Server Agent viz SSMS, then I created a management plan to do full backups on our SQL server instance, and scheduled it for daily operations. However, when I manually ask it to execute that job - to ensure all is working correctly - I get the error: SQLServer Error: 15404, Could not obtain information about Windows NT group/user 'WIN-443PT0LULQU\Administrator', error code 0x534 That sounds to me like an NT permissions issue - that whatever it is - XP Agent? - attempts to retrieve the permissions of the aforementioned user - and that fails. Part of what is bizarre here - is there is not machine 'WIN-443PT0LULQU' - that doesn't exist - WTH is SQL Server forcing that in there for in the first place?! I want this to run as the Administrator - on the local machine 'BUILD-SERVER' - not that garbage name it keeps forcing... I'm way out of my depth here and this whole process is crazy-making. How in 2018 is it not possibly to click a few wizard NEXT style buttons and configure Windows / SQL Server to back its freakin' self up regularly correctly?