Missing audio

My sister, who lives 100 miles away, gets video but not audio on most
of the URLs that people email to her. For example on:

http://yeli.us/Flash/Fire.html (Great fun video, BTW.)

Any ideas what software she is missing? Shockwave? Real Audio?

Files with a .wmv or .wma extension seem to work OK.

BTW, it is a Dell computer and she is a newbie to computers.

Thanks.