MBSA Reporting an Unknown Third Administrator Account

[Alan]

The Microsoft Baseline Security Analyzer (MBSA) is reporting that
there are 3 administrators on a PC (Win XP SP1 Home Edition) that
I recently had to clean of pests: Administrator, User1 and
S-1-5-21-2163411867-891307005-2424629274-1003. Booting in safe
mode shows only two user accounts: Administrator and User1.
Anyone know what this third account may be? Is it something I
need to worry about?

 

[Nepatsfan]

I vaguely recall seeing something similar to this where a user
account wasn't deleted correctly. I believe the fix was to go
into Control Panel -> System -> Advanced -> User Profiles ->
Settings and delete the profile matching that SID.