I am unable to hear or see a WMV File

Hi! I need help on playing Windows Media Video Files on my Windows XP computer. I could not play any WMV files on my PC. My system is running Windows XP Professional Service Pack 3 with Windows Media Player 11. The rest of the programs and software are up to date so I really don't know what else to do to fix this.
There is no error shown on my screen. I have searched on the net and learned that I need to download or re-install the software package for my WMV. But I could not figure how to do it.
Please help me.
