Well...if you want to keep your new files separately, simply add a rompath and store your new roms there.

If you want to know which sets have been changed or are newly added, you can go various ways.

I personally do it this way:
- set all current sets to file attribut -a (and/or time/date something like 01/01/2003 00:00)
- disable Settings->preserve archive date/time
- scan and update your collection to the new mame
- the sets with +a (and/or changed date/time) are the new and changed ones.

Roman Scherzer
ClrMamePro