Let me explain everything.
First,even without Inferno,I couldn't listen the mainhall sound in the normal mode.I've played with the Neo Terra campaign,that required the raynor model i don't have. I have put the INF main file on the FS2 folder,and since that moment there is only Inferno.Only.Put the INF Main in another folder,and the CPU doens't find the <vesuvius.pof>.FRED works only with the Inferno models.And that's not all:the Inferno ships had no weapons(problem I've solved about yesterday).
I don't know what to do,if reinstalling the game or uninstalling it and then installing again.Inferno is beautiful,okay,but with only 15 missions in the 1st chapter I don't have so much to do.My created campaign also requires the normal mode.I don't know what LGM means,but I think that what Flipside said is true.