"expressInstall & swfobject.js & flv & html page in the same folder"
but did not mention the player .swf file, the actual video player. Have you uploaded the skin or player .swf also?
Have you included a link to the swfobject in the head? something like this:
By the way, there is no techincal need to have all the files in one folder. You can place the individual files in whatever folders you want as long as you use the correct relative path to gather all those files into the html page.