Help about my laptop!?

Well i have a Toshiba laptop and have Windows Live Movie Maker but when i try to add my own music, it doesn't play it. The only music it will let me play is the sample music. E.g. If i wanted to put and Avril Lavigne song onto my movie, it wouldn;t let me so i would have to play either some clical music or a jazzy boring piece that doesn't go with my movie. Please help :s Lindy xx