> I am finding that I ClrMamePro is creating additional Roms that I did not have
> loaded to begin with. Why would that be?
>

Looks like you talk about the rebuilder. It's a normal and intentional behaviour, since the rebuilder rebuilds anything it finds. If a rom is shared by 20 sets, it will create all 20 set (with at least that shared rom). The rebuilder documentation shows you exactly how it works.
Fixmissing on the other hand only tries to fix the current set which got a missing file.
No other files are created.

Roman Scherzer
ClrMamePro