Transfer the song on to your computer if it isn't already on it. Most computers come with built-in CD-ripping applications as part of their media suites. If you are using Windows Media Player, for example, you can insert a CD and click on the tab that says "Rip CD."
Obtain a sound-editing program. Most computers already have a simple sound editor included. If yours doesn't, you can download a free program such as Audacity.
Open the song with your sound-editing program, and reverse it. In Audacity, you would click "Edit > Select All" to select the whole song. Then, click "Effect > Reverse" to reverse the direction. Hit the play button to hear the song.
Upload your song to a website that reverses playback direction, such as Talkbackwards.com, if you prefer. It will automatically play the song back in reverse.