Christopher,
I'm wanting to change the sound set in my Conrail ES44AC - Is it the same as it was in PS2?
Yes, it works the same way.
Which sound files work in the PS3 engines?
Either PS3 sound files or 3 Volt PS2 sound files will work.
When I had PS2 stuff I did it all the time & it was cool. Not seeing much out there about doing it with PS3.
Also - does the loader software run on Win7?
If you did this "all the time" with PS2 engines, then you'd know that the Loader Program runs (only) under Windows.
This and a whole lot more is all in MTH’s “The DCS O Gauge Companion 2nd Edition", available for purchase as an eBook or a printed book at MTH's web store!