This website contains free music downloads that you can use in your digital presentions like MS PowerPoint or PhotoStory3:

http://incompetech.com/m/c/royalty-free

 How do I place a credit for this music in my project?  

 If your project has only music from me in it; you can credit it as "Music: Kevin MacLeod".
If your project has many pieces from different people, you can credit me as "(name of the pieces of music you are using) Kevin MacLeod (incompetech.com)".
If you'd like to include the full license for legal reasons, you can do the following: "Title Kevin MacLeod (incompetech.com) Licensed under Creative Commons "Attribution 3.0" http://creativecommons.org/licenses/by/3.0/"