Another reason not to "borrow" music from other projects, be that a movie, anime or video game, is that people watching it will be sucked out of your project and say "Hey! That's the music from ______." You will lose them while they think about the music you "borrowed" and not your storyline.
I recommend you first try to get original music. You may be able to find someone local who can compose an original score. It's great because nobody can find your music anyplace but on your movie. Something I don't like to do, but have had friends do is they use music from other movies as a temp (temporary) track during editing and them have a composer do a score that sounds like the temp music, but not enough to get sued. My problem with that is if I hear music like that, then I get pulled out of the movie trying to figure out what movies they used in their temp track.
You can use one of the loop-based music programs like Acid or Apple's soundtrack to make soundtracks. They're very cool, but it's hard to compose a full-blown orchestral soundtrack.
In the end, using music from other project is stealing, don't do it. If you get caught you could get sued and it limits where you can show your projects.
Scott