Help with FLV!

Hi there,
I need some help with flv files. I import them to stage, in flash 8, I test the movie and they work properly, but once I upload the movie in the internet, the flv files won’t play. If anyone could tell me what to do, or how to make the flv files play in the same window, or in a new window, but the new window must be the size of the flv file.
Thanks!