Does the word Promethean need to be capitalized or lower case letter?

It is called a promethean board.

IF you are refering to the works of Prometheus, then it is capitalized. If you are refering to other meanings, it is not capitalized.

Ok I refering to using it

so it should be capitalized

The word "Promethean" should be capitalized as it is a proper noun, referring to a specific brand name or trademark, such as "Promethean board."

The word "Promethean" typically needs to be capitalized. The general rule is that proper nouns, which are specific names of people, places, or things, should be capitalized. "Promethean" is a proper noun because it refers to a specific brand of interactive whiteboard called "Promethean Board." In this case, "Promethean" is the brand name and should be capitalized.

However, when referring to a generic interactive whiteboard of any brand, you would use lowercase letters. For example, you correctly wrote "promethean board" with lowercase letters because you did not specify a specific brand.

In summary, when referring to the specific brand "Promethean Board," capitalize the word "Promethean." When referring to a generic interactive whiteboard, like any brand, use lowercase letters.