there are a couple of free porgrams you can use online (or at least have a free trial of). The Adobe Audition is what I reccommend, or if you have/ have access to a MAC, use Garage Band.
Free trial of Audition and then go to the box on the right titled "Next Steps" and click "Try Now." That should be good for a few weeks, you have to register, and figure everything out, but it's worth it.