converting music files

I am new here so I don't even know if this is where I am supposed to ask this question. I want to make a slide show with my own music. I have some special songs to put with the pictures. How can I get them converted to the format to use them with Windows Movie Maker?

Any help will be appreciated! Thanks

 

A simple program you may try would be DVDSanta.

 

Thank you!! I'll try it.