There are a bunch of issues about that on the adobe.com RoboHelp forums. I think the problems are mostly Microsoft's fault.
https://www.google.com/search?hl=en&safe=off&tbo=d&q=+site:forums.adobe.com+embed+video+chm&sa=X&ei=3X0JUdruJej7ygGHqoCYBA&ved=0CFMQrQIwAw&biw=1680&bih=933
