FF7 is not multithreaded, at all. It will have no perceivable benefit from running on multiple cores, and in fact could potentially run worse (Windows attempts to split tasks into separate cores for a performance boost, but it's not always good at it). Honestly, since this game is so limited in requirements anyway, the performance "boost" of multiple cores isn't really worth it.
However, as Vgr said, FF7Music (or any mod which runs a separate application or process) could benefit from properly set affinities. But not really, because FF7 + Aali's Driver + FF7Music still has really low requirements (my 1.7GHz pentium 4 laptop from 2005 can run it just fine with these mods, for example).