AHHHHH! Computers!!!!

I'm excited that I added music and everything but the computer is being sooooooo slow! It's been freezing up and taking forever. I love computers and all, but they can be such a pain. The song and video I added are great and all, but they don't play the way through. They keep stopping like every 3 seconds and it doesn't play all the way through. I would rather have it take a while to load and play it all the way through then start sooner and mess up during the song. Please help me if you know how to fix this problem!!!