Instale o codec Real Alternative. Isso deve resolver o problema:
You do need a player that is capable of playing RealMedia. The included Media Player Classic supports it and works very well. Supported: RealAudio (.ra .rpm), RealMedia (.rm .ram .rmvb .rpx .smi .smil), RealText (.rt), ReadPix (.rp), RealMedia embedded in webpages. .smi and .smil files sometimes only play the first part of a clip. This is a limitation of the current Media Player Classic. The RealMedia Browser plugin supports Internet Explorer, Opera, Netscape and Mozilla.