questions - What's the difference between なんと and どう

I'm having a lot of trouble working out the difference between なんと and どう。 どう is "How" e.g. これはどう書きますか "How do you write this?" and is easy for me to understand. The problem is なんと、the dictionaries translate it as "how?" and "what?".

If I want to say "how" when do I use どう and when do I use なんと and What's the difference between これはなんと書きますか and これはどう書きますか。To put it in context, if it helps, I'm studying JLPT2 but still have problems with this.

Answer

どう can be paraphrased as "in which way", "in what manner". なんと cannot, and it means "as what".

これはどう言いますか。

(literally) 'In what manner do you say this?'
'How do you pronounce this?'

これは何と言いますか。
(literally) 'As what do you say this?'
'How do you call this?'