Help Wanted!!! NIS threat: (Trojan) mythxpak.exe in a compressed folder (Age of Empires II)

Norton couldn't remove it when I tried, neither has it been able to quarantine it as it comes up as Unresolved.  I've downloaded Malwarebytes but that didn't even pick up the problem even though I did an actual scan of the folder.

 

If I use the FileAssassin tool on Malwarebytes will that be enough to solve the problem?

 

This darn thing was identified on my pc about a month ago even though it was downloaded ages ago.  It's classed as a high risk by Norton's.  

 

Thanks  for your help.