I've found a file on some of my machines called 'SETUP.SUS'.  Is this file related to SUS in anyway?

Contributed By: Cliff Hobbs [MVP SMS]
No.  The file is included on the MS OS/2 and MS-DOS Macro Assemblers Setup disk which it looks like someone has copied to your machines.  This file contains the information used by the Setup program ('RUNME').  You can do a quick check to see if this is the same file by editing it. The first line should be:

CLS a: 30 "Microsoft(R) MASM 5.10 Setup"