07-31-2006, 07:23 PM
Sounds like you are playing Single Player, in which case you cannot play in NM or Hell Mode. (Actually there is a way, but you would not be able to access NM mode unless you have a multiplayer character of sufficient level.) Now that you are familiar with the game, you may just want to start a multiplayer character and log onto battlenet or use the direct connect option. You will be given the option of choosing difficulty levels if you do that, provided your character is high enough level. (20 for Nightmare, 30 for Hell)