Unexpected file format..again

Why am I posting a question which has been asked a million times, because the question is never answered correctly millions of times, least according to google:smirk2:

DeePixel has just finished a magnifico website for me, and sent me the .fla but as you imagine when trying to open it “unexpected file format” and he is not availble now and I need this done urgently, I used Flash MX, how do I fix this?

Thanks!