Cannot update Window Media!! Arghh

I need to make sure I have the latest windows media player on my computer as a few different third party applications which play through WMP do not work. When I contact the third parties they said to download the latest updates since that is likely the cause of the problem. When I update the 'Update for Windows Vista for x64-based Systems (KB941651)' it says The update does not apply to your system. Now I know for a fact I have the 64 bit system since I've checked this under the computer properties and I had to know for other software I had to download. Why am i getting this error?? Please help.