This Apple ID has not yet been used with the iTunes Store. This message keeps coming up and when I follow the process asks me for credit card. I do not want to buy anything. I just want to download free apps.

unless the instructions on this page are followed when creating an account : Create an iTunes Store, App Store, or iBooks Store account without a credit card or other payment method - Apple Suppor…

then credit card details will need to be entered before the account can be used to download any item from the store, including free items - you should be able to remove the card's details after entering them.

I am really annoyed by the fact that I have verified my account but the error that I have used my apple id in app store persistently shows when I try to format my mac book air. It doesn't happen to my macbook pro but only to my mcbook air.

I will be using my macbook air to build apps so please can someone help me why the heck is this happening?

Can you explain what the 'error' is in more detail please.