Quick Time won't play SMIL files

Deborah, welcome to these discussions.
Many of the .smil downloads are set to use QuickTime as the default player. But many also use the .ra (Real Audio) format and QuickTime Player gives an error message.
Find one of the downloaded .smil files and open the Get Info window (Command-I).
Look at the little disclosure triangle next to "Open With" and use the pull down menu to pick Real Player. If it is not on the list choose "Other" and then navigate to the Real Player app. Then click the "Change All" (and confirm your change).
They will now open using Real Player.

Sorry. Maybe I wasn't clear.
Use the Finder's "Get Info" window (not QT Player).
Navigate to wherever your downloads go. Find a .smil file and click (just once) to highlight it. Then Command-I will open the Get Info window you need.

Deborah,
I had exactly the same problem, but also could not find the
"get info" window in OS 9.1 to change all of the .smil files from NPR. So I just opened my "Real Player" application and under file-open, chose the NPR.smil file that I had saved (downloaded) to the desktop and it opened and played it without a hitch.
Thanks so much for asking the question.
Dave

I am having similar problems except with Real One files. I download an archive file from NPR which is a Real One file. When I go to "get info", it shows Real one as default. When I play the file, there is no sound. any suggestion?

Thanks-

Robert,
As I mentioned earlier, when I could not open an MPR file (all of which seem to be .smil files now) I just opened my "Real Player" application and under file-open, chose the NPR.smil file that I had saved (downloaded) to the desktop and it opened and played without a hitch.
Hope this helps,
Dave

At this site
http://www.npr.org/rss/podcast/podcast_directory.php
Many of the shows are now podcasts that you can set up iTunes to download and listen to at your leisure. The shows that I don't think you'll find there yet are the longer format shows (due to bandwidth considerations) but it's definitely a step in the right direction (as there's never a dearth of programs that play .mp3's).