Why wont my windows media player work?

I have had this computer for almost a year and it still works great. but just recently, every time i tried to open windows media player or tried to play a file on windows media player it gives me an error message that says"the file wmp.dll has a version number of 10.0.0.4058 where 10.0.0.4036 was expected. windows media player is not installed properly and must be re-installed." then it asks me if i want to download it from the website. after i try to download it from the website it gives me another error message saying, "this application has failed to start because pdh.dll was not found. re-installing this application may fix this problem". i have no clue what any of these files mean. if someone could tell me what they mean and tell me how i would stop this messages from coming up, that would be great!