Yes here's a showcase of preloader examples. Scroll down and click on the images to see what the preloader looks like. They basically perform two functions.
1. Entertain the user while the movie is downloading
2. Inform the user the progress of the download
Once the download is complete, the flash movie loads and the preloader disappears.
I often set the output quality to the best before conversion, so there is nearly no loss after conversion. I have tried to insert YouTube video and Flash to my presentation, the converted Flash movie is good, and the video is embedded to my presentation, also plays well. You could have a try.
a dirty kludge to make files appear to load faster than the connection speed allows
ignore image, its just you have to load the file for "something"
puts enough of swf or mpeg into the buffer before the button is clicked that play begins immediately
viewers forgive a lot if they dont see the waiting sign