What causes Windows Vista Home Premium's Windows Media Player to have playback problems?

I purchased a Dell Inspiron 6400 laptop from Dell Malaysia in April 07. Whenever I switch to a different song e.g. Jingle Bells to We Wish You a Merry Christmas, it takes about one minute to change. Also, if I have a playlist of two songs e.g. Rudolph the Red Nosed Reindeer and Frosty the Snowman, the transition from one song to another is very poor. The song becomes very choppy during the ending of the song. What's the problem?