Administrator WMP 11

Hi , i'm having trouble with WMP11 . Not sure how it happened , but when i click on the wmp 11 icon a message comes up saying " to finish installing wmp 11 restart your computer and then log in as administrator or as a member of an administrator group " . i have done that , but still will not work . I have changed my administrator password but that didnt work either . I already had wmp11 on my computer so not sure whats going on . Also noted that when i try to make itunes my default it says that i " dont have enough access privileges for that operation" . Probably a related problem .Hope someone can help