I am playing a game where I am a queen, a bishop and three pawns up. I also have mate in seven. But the other guy is not resigning. Is there some breach of etiquette? I don't want to say something wrong, as that may spoil the victory. I also don't want to look arrogant. Should I say something???

Some players (especially beginners) play to the end.  I don't think there's a breach of etiquette.  It's another issue if he deliberately time forfeits instead of resigning.  But always give the benefit of the doubt to your opponent (unforseen circumstances).

Thanks for the advice, I guess it's usually me at the other end. Anyways, he resigned.