So if i understood well, it would be like this, for example:

<object width="425" height="350" type="application/x-shockwave-flash" data="http://www.mywebsite.com/main/player/player.swf"><param name="movie" value="http://www.mywebsite.com/main/player/player.swf"><param name="flashvars" value="&allowfullscreen=true&file=http://www.mywebsite.com/main/flvideo/1227190362701587644.flv&height=350&image=http://www.mywebsite.com/main/thumb/16.jpg&width=425&location=http://www.mywebsite.com/main/player/player.swf&logo=http://www.mywebsite.com/main/templates/images/watermark.gif&link=http://www.mywebsite.com&linktarget=_blank"/></object>

The &allowfullscreen=true has some space between "&" and "allowfullscreen=true"?