LeMarchand is probably right, you probably don't have the right media player or codec. Codec means COmpression DECompression and is simply a piece of software that converts the signal from the internet into a picture and sound that you can watch on your pc. It is can be likened to digital TV. You can't watch didgital tv without a digibox. I would suggest that you download the completely free 18.1mb Media Player Classic from
http://www.k-litecodecpack.com/ (select the screen) This will replace Real Media, Windows Media, Quicktime, DivX, Xvid etc etc as your media player. Why have three when you can have one very good one? As an added bonus you don't get the spyware and undeletable installation you get with some media players