A file with the extension .rm is a Real Media file. I don't know if you can read it with another player than Realplayer.
I use the software "NetTransport" to recorde video which are broadcoasted in livestream.
You just need to find the URL where the video is. For that, you read the video on the site, you make a right-click on it and you find the URL in the properties. Generally it works. But if you don't find the URL in properties, you must right-click in the window and choose "View Source". In the window which appears, you're looking for the URL.
When you've got the URL, you copy it in Net Transport (New/source/URL) and you can download the video !
I'm not sure my explanations are very clear
but I hope that it helps you.