Are you sure? I recently did that, and Doom95 does that no matter which operating system it is on. The problem with most of the errors lies in the Doom.wad and Doom2.wad files. Same thing with TNT.wad and Plutonia.wad. Those errors do not occur during normal gameplay, because you have to manually type something in the game to cause them. I generally avoid typing "IDMUS00" if I'm playing any Doom game in that program or any other Doom game. At least I have Deepsea. Maybe I can insert d_introa into the .wad and fix the issue. It's worth an attempt, wouldn't you say?
EDIT: If you want to reply, go ahead, but I think there's no fix for this problem. Appearantly, d_introa.mus played when I typed "IDMUS45" in Doom 1. "IDMUS00" apparantly is supposed to do nothing but produce a message that says "Impossible Selection".