Vista - Windows Media Player not playing?

Help....
I have some .wmv files that I would like to watch. (dirtbike riding stuffs)
I have watched these movies in the past but now all of a sudden I click on the files and Windows Media Player opens up like it's gonna play the clip but nothing ever happends. Nadda, Zero...nuth'n
This also applies for .wmv files off the internet.
(I've tested with many .wmv files and media player always opens up like it's gonna play but never does)

It has worked in the past.

I have Vista Business x64 sp1
I've tried to reinstall windows media player but I get a message telling me I already have the latest version instsalled: 11.0.6001.7000
I downloaded this, Windows Media Player Software Informer: Latest version download, news and info about this Microsoft Corporation program. Expand your horizons in the field of playing videos., which says it's version 11.0.6001.7000 but I still get the same error message.

I googled fix's and such but nothing I tried has helped out.
Tried reinstalling SP1, won't let me, says I have it installed already.

I'm not that great with Vista in regards to uninstalling media player (if that's possible) in order to reinstall it.
If someone can help me out here, I'd much appriaciate it.

Thank you.

2 slow u people R ....I installed VLC media player for now.

Do you have codecs? I would recommend the Vista Codec pack. I can play anything
I get on the WMP right now. You will have to install the 32bit version of it first in the Program Files x86, then 64bit components in the Program Files .Please try it, here is the link:Shark007's Codecs Homepage