Is it permissible to legally change your first name?

I would like to know whether or not it is permissible in Islam for someone to change their first name (regardless of circumstance)? When I say change, I mean formally as opposed to informally. I do not have enough knowledge of hadith to ascertain the answer for myself, so your answers will be much appreciated. I'm primarily after a general 'Sunni' view on the matter. Thanks.