I could be wrong here but having been doing a similar thing recently. The codec h.264 will only play on quicktime 7 I beleive. What I did and its really easy is buy flip4mac and turn the quicktimes into wmv files. These will be compatible with pcs. If pc users download quicktime 7 there seems to be some incompatability problems with video for windows. So by adding one of each will hopefully cover you for most computers.
you can have a look to see what I’ve done if you like