problem with windows media player--please help

hey guys
i'm having a pretty irritating problem with windows media player--when i try to run wmp,nothing happens.so i tried to rollback to the old version,it said that rollback was completed and then again i tried to run wmp nothing happened.there is no process running in the background and then finally when i decided to reinstall wmp 11 back, it said "internal error".plz plz help.
thanks