The location of video file is "relative" to the location of the "player". The correct coding is:
<embed src="skin1/images/custom/player-viral.swf" width="400" height="300"
bgcolor="#FFFFFF" type="application/x-shockwave-flash" pluginspage="
http://www.macromedia.com/go/getflashplayer"
flashvars="file=videofilename.flv&autostart=true" width="400" height="300" /> </embed>
Chris