Cant play audio with WMP11???

I use WMP 11. My computer suddenly can not play audio files as well as video files. It appeared on the screen that "...The player might not support the file type or might not support the codec...". But when I used JetAudio to play the audio files, it still worked well. However, JetAudio can play audio files only, it can not play video files due to the missing of some codecs. It's obviously weird cuz the files I wanted to play were the supported types (mp3, wma, wav, avi, wmv, mpg....) I have no idea what happened to my com. I uninstalled WMP and reinstalled it but nothing happened. I even reinstalled the sound card driver but it did not work, either. Pleaze help me to solve the problem.