File Extension NTH File Format Nokia series 60 Theme Studio for Symbian OS theme file NTH stands for Nokia series 60 Theme Studio for Symbian OS theme file. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question Upgrade step from win nt and win 2000 to win 2003 Symbian, S60, UIQ to be updated Which Smartphone Platforms Survive?