User accounts frozen and new one created - ESET issue

Hi Guys.
My ESET was recently flagged up as not running. When I tried to restart it, it said I had the wrong version for my OS (7 Home Premium 64 bit). Re-downloaded and installed with no issues. An hour or so later the two user accounts on the machine came up as being time restricted and would not let access. Also a new password protected user named --666-- appeared. I immediately panicked and disconnected the modem cable. I've since formatted the drives and re-installed 7. Was this a virus?

its the devil! it may have been a virus, or it may have just been a hidden user account that was created by a piece of software. I cant see anything online about it but if it was a virus its been wiped off now

I couldn't find anything on Google except the hoax Youtube thing. Didn't have any new software loaded so can't see why a sudden hidden account. Also strange it occurred with an ESET problem. Just wondered if anyone else had experienced it.