I have a Kindle2 and I want to put music on it, but I don't know how, or how to make an mp3, any advice?

I have never converted cds into mp3 files. Can you do that with windows media? I am a little suspicious of going to sites I don’t know to find the free software, because I don’t know which ones are trustworthy. Can anyone help? Has anyone else put songs onto a Kindle2? Thank you for your time.