Poorly designed save systems

I recently fired up Assassin's Creed: Altaïr's Chronicles on the DS with the thought that I was going to try and the game. All I need to do is run through the game on hard. You have to complete the game once in order to do so, which I've already done. So I clicked the New Game option was given the standard warning about loosing my existing progress. I clicked yes, and was presented with a difficulty selection screen. Hang on, the Hard option was greyed out!

Grrrr! now I've got to play through the game again on Medium just to the game.